"house of cards," when the killer tells his wife. >> the best way to succeed is to write what you know. >> and i'm natalie morales, and this is "dateline". at night, this is absolutely pitch dark. >> reporter: it'd been abandoned and it was secluded. this was his playground. >> this was the place we'd been searching for. >> reporter: it was in the still of the night when the killings started. >> i've been shot, me and my mother have been shot! >> you can feel and hear the fear in her voice. >> reporter: a single mother and her teenage daughter, ambushed in their bedrooms. >> here comes a monster into your house. >> i just broke down, you know? i just couldn't imagine who would want to do this?

>> reporter: then, it happened again to another mother, another daughter. >> somebody's killing mothers and daughters? that's about as scary as it gets. >> as scary as it gets. >> reporter: who was out there? and who would be next? >> it's something you would never imagine would happen. >> reporter: the clues would lie here, an abandoned mansion, eerie. haunting. where was this killer hiding? >> cold, calculating eyes, lifeless. he was almost a ghost. >> reporter: could they catch him? could they stop him? >> i get chills all over. i'm kind of on the edge of my seat. >> he truly thought he could outsmart us. hello and welcome to "dateline." would you recognize danger if it was lurking nearby? this story that you're about to hear is a tale of true terror, a

killer was stalking victims in a quiet neighborhood leaving residents panicked that they would be next. police were determined to catch him unaware he was hiding in plain sight. but soon, a stolen set of keys would help investigators unlock this mystery and unmask a murderer. here's dennis murphy with "the unusual suspect." >> reporter: consider for a moment the cozy word "home," and all it evokes. warmth. family, shelter. security. got it? and now reflect on what happens when those four walls are breached, when nightmare stuff crawls through the window, kicks in the doors. when a haven becomes a house of horrors. so how does that feel? just ask lloyd irvin. >> i'm laying on the couch. i wake up and there's two gunmen over top of me holding guns, pointing them at me, like, holding down. "you're being robbed.

don't move." >> reporter: almost eight years have passed since that night in august 2008, here outside the nation's capital in a nice neighborhood in prince george's county, maryland, but lloyd and vicky irvin and their son, just 4 years old at the time, are still haunted by the image of the gunmen. two masked intruders. >> talk about your worst nightmares. this is it. >> yes, it's something you would never imagine would happen. >> reporter: what the robbers didn't count on was that lloyd is a nationally- renowned martial arts expert. and when one of the gunmen walked away to scope out the rest of the house, lloyd was suddenly one-on-one with his accomplice. >> gunman's over here in the corner, huh? >> right in the corner right there. i know he doesn't have any room to back up at all. i just go. i'm coming over here. and i got the gun. i'm trying to get the cartridge out. and once i get the cartridge out, i -- it drops. so i hit the ground. >> where's the intruder going? >> he ran out the room. he was running low like, he has the gun. get outta here. he has the gun. >> reporter: by the time lloyd managed to reload the wrestled-away gun and give

chase, both home invaders had escaped. >> and i'm calling 911. and my son's on top of me. and he's just shaking, not saying a word, not crying. just shaking. and i often think, you know, were they going to kill us that night? >> reporter: the irvin family wouldn't be the first, or the last, to ask that awful question. >> i'd like to report a robbery, armed robbery. >> and they had a gun... >> prince george's county, 911, how may i help you? >> someone broke into my house, i see the back window. >> reporter: in the months that followed, the area was hit with a wave of home invasions. each time two masked men, meticulous about not leaving fingerprints or evidence behind. the prince george's county police were baffled. the community, understandably on edge. and then, on january 26, 2009, on a quiet street in upper marlboro, the county seat anxiety turned to full-on, bolt-the-doors panic. >> prince george's county 911 center. what is your emergency? >> ma'am, i've been shot. me and my mother have been shot.

i'm bleeding to death. >> where are you? >> reporter: it was a desperate plea for help from a dying girl. on the phone, 16-year old student, karissa lofton. >> sweetie, slow down. what's the address? >> reporter: police rushed to the scene, but it was too late. they found karissa and her mom, karen in their bedrooms. each killed execution-style with a shot straight to the head. >> crimes quickly become statistics. but this just stands out, doesn't it? >> it stands out. it makes the hair on the back of your neck stand up, also. >> reporter: veteran prince george's county homicide detective bernie nelson was in charge of the case. the first arriving officers told him they'd found the main door locked shut from the inside. the killer, they thought, had likely entered the house through an unlocked side window. >> this bedroom on the second floor that's facing us, that's where karissa was found. >> reporter: detective nelson wondered, did the murders have anything to do with the plague of recent home invasion

robberies? if so, why was nothing stolen from the house? >> her vehicle was still in the driveway. nothing appeared disturbed. >> reporter: investigators didn't find any useful forensic evidence. just six spent shell casings from the bullets that had killed karen and karissa, fired from a glock 17 handgun. >> we did find out that just two doors down across the street, someone had seen a blue vehicle parked right down on the right side of the road. and that, right now, at this point, that's all i have. >> reporter: so detective nelson set out to find out more about his victims. karen lofton turned out to be a devoted mother and nurse with no apparent enemies. she was divorced from karissa's father, kirkland, who now lived in atlanta. the daughter, karissa, was in private school. good grades and still very attached to her father. >> karissa was always a special girl for me because at a young age, she had open-heart surgery. and she bounced right back from it. >> reporter: kirkland says he

had watched karissa blossom into a gregarious teenager, a fashionista and aspiring model with a knack for selfies. >> i sing this song by bob carlysle called "butterfly kisses." it told the story of him and a daughter. and i used to sing that song to her. and she would just look up at me and she loved me singing that song to her. she was my butterfly, that's what i called her. >> reporter: now kirkland's butterfly was dead, and detective nelson recruited some of pg county's finest to help him solve the case, including detective anthony schartner. >> this is a mother, hard-working, and her daughter. you know, both think that they're safely inside their home. >> and here comes the guy out of your worst dreams. >> yep. >> here comes a monster into your house. >> and he's got a glock. >> it shocked us all. >> reporter: as the hunt for this brutal killer went into full gear, detectives started as

they always do, with the usual suspects. >> since there is no rhyme or reason behind it that you can come up with, you have to look at family members. >> reporter: and one family member in particular, karissa's 20-year-old brother, kion. he lived in the house, too, but he wasn't there when cops arrived. police spotted him near the crime scene several hours after the murders. could a son, a brother, have done such a monstrous thing? >> the investigation begins with some tough questions for kion. coming up. >> would you have hurt your mom and sister? >> one of the detectives blatantly said everybody in that room thinks it's you. >> was it? what happened next would launch a whole new wave of fear when "dateline" continues. with soothing honey-licious taste. nyquil honey. the nighttime, sniffling, sneezing, coughing, aching, stuffy head, fever best sleep with a cold medicine.

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>> reporter: a mother and her daughter, executed. detective bernie nelson had investigated hundreds of murders. had learned to keep the recurring images of death at arm's length. but this case was different, he was a father to a teenager around karissa lofton's age. >> ma'am, i've been shot. me and my mother have been shot. i'm bleeding to death. >> that poor little girl in her bedroom. she has the gumption to get on the phone and call you. >> it hurts to listen to the 911 call because you can feel and hear the fear in her voice. >> reporter: even though nothing

was taken, it seemed clear that the killer broke into the house. in fact, the burglar alarm had gone off, but it was disabled in under a minute. and that put karen's son, kion lofton, at the top of police's person-of-interest list. he lived in the house. he knew the code. police brought him in for questioning. >> does your mom set the alarm for the house? >> mm-hmm. >> okay, all the time? >> every day. every time. >> one of the detectives, blatantly said, you know, "everybody in that room thinks it's you. you are the only one who had access to the pin code." >> would you have hurt your mom or sister? >> no. >> you would never hurt your mom or sister? i was upset. you can do whatever you need to do. it's not me. keon told investigators he was spending the night at his fiancee's house. house, when her mom woke him up and told him she'd heard on the news that two women on his

street had been murdered. >> i just ran out the house. my heart's racing. i don't even open the gate. i just hop the gate, hop in my car. i'm just -- i'm running lights. i'm speeding. i'm still calling at the same time. and when i got there, they asked me for my name. and i was, like, "i'm kion." and the police officer just turned his head. and he kind of looked into his radio and said, "okay, we got the son here." and i just broke down, you know. >> reporter: kion's alibi checked out. it wasn't him. investigators also interviewed kirkland, karen's ex-husband, and karissa's father. he too had an airtight alibi. he'd been in atlanta at the time of the murders. you go next on detective nelson's list was karen's former boyfriend, michael lacey. he'd refused to take a lie detector test, so plolice interviewed him three separate times. >> y'all have keys to each other's house? >> definitely not. >> you could go over and walk in? >> we would call. >> he's someone that we had to rule out completely, and we did that. >> so if you're thinking in your line of work, the usual suspects, the usual suspects weren't going to figure in this one.

>> not the immediate family. >> reporter: detectives nelson and schartner realized they had on their hands what homicide cops hate, a true mystery. >> the first 48 hours of a case. usually, you get a break. and there's something that says chase this, right? >> yes. normally you would get something in the first 48 hours. >> so this is as baffling as it is cruel? >> exactly. it didn't make any sense. >> reporter: then came march 16, 2009, six weeks after the lofton killings, when two unsolved murders became four. it began with a report of a stolen nissan maxima just a couple of blocks from where the loftons had been killed. >> what's the nature of your emergency? >> i just left my house about an hour ago and came back. my car is missing out of the car port. >> reporter: detective schartner was on call that night. >> she's on the phone with the 911 calltaker, she notices that her car comes zooming by from up here on the street, and comes by her at a fast rate of speed. >> that's my car. okay, it just zoomed past me.

wow! >> she sees it while she's on the phone with dispatch? here it comes. there it goes. >> absolutely. >> reporter: police swarmed the neighborhood hoping to nab the car thief. he was nowhere to be found, but police soon discovered the stolen car. captured here on one of the cruiser's car-dash cameras, it was parked in the driveway of a vacant house, engulfed in flames. fire fighters called to the scene to extinguish the fire made a grisly discovery. two bodies burned beyond recognition. and the victims? another mother and her teenage daughter. dental records confirmed the identities of the two female bodies found monday in the trunk of this stolen car. 42-year-old delores dewitt and her daughter, 19-year-old ebony dewitt. >> she worked at a nursing home. and she loved taking care of the elderly population. i mean, she loved those people. and they loved her. >> reporter: patricia smith remembers her sister delores as a mother and nurse who worked

hard to provide a good life for her two daughters, but always saved a little time for herself. >> she liked to go places. every year she would treat herself on vacation. she felt like she worked hard, she should play hard. >> reporter: and ebony? she was the live-wire at family get-togethers. >> we made everybody laugh. we just make the party live and just act crazy until the end of the day. i mean, she -- she loved life. >> reporter: the last person known to have seen ebony alive was her boyfriend. he told detectives that the previous night they'd had a late dinner. she was wearing her favorite blue sweater. then he drove her home, watched her go inside her house. the killer may have been waiting. and now, when police once again made no arrests within 48 hours of the murders, waiting too was a devastated patricia. >> i started going back to my sister's house. late at night, i would go and sit in the yard just hoping that he would come back. and i would sit there with the knife in my hand. and i will hold -- i will hold

it like real tight just in case he came up on me or something. 'cause it would be him or me. either him or me. and i told the detectives what i did. >> she couldn't sit still and do nothing. she wanted to be involved in the investigation from day one. she would actually go door to door in the neighborhood and talk to neighbors, try to ask them questions. but i had to repeatedly explain to her that we can't have her interrupting our case. >> she's a thorn in your side. >> she is. but i understood because if my sister were called, it would be hard for me to sit still too. >> reporter: so detective schartner made patricia a promise. >> we were sitting in the car. and i remember just crying and crying and crying. and then he promised me, he said, "i'm gonna get him." he said, "if it's the last thing i do, i'm gonna get him." to do that, detectives schartner and nelson had to confront a terrifying question.

>> you got two murdered mother-daughters within, across the fence, virtually. >> right. >> same neighborhood. so you're thinking, "are these things related?" right? >> you have to think that. and if they are related, you have a serial murderer on your hands. and you don't know when he's going to hit next. and you don't know who he's going to hit next. >> coming up. >> a neighborhood on edge. police under pressure, and the question everyone feared. would there be another victim? >> it was wide open. we had nothing. that's when it gets scary. >> when "dateline" continues. who else reads books about submarines? my dad. yeah. oh, those are -- progressive can't protect you from becoming your parents, but we can protect your home and auto when you bundle with us.

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>> reporter: prince george's homicide detectives, bernie nelson and tony schartner, hoped their collective experience would help crack two of the most horrific murder cases they'd ever encountered. >> when you back up and look at what you got, the scary fact is somebody's killing mothers and daughters, right? that's the commonality? >> yes. and with the close proximity of where the dewitts were found burned in the vehicle, it was just two blocks away from where the loftons were shot in their house. >> reporter: the detectives suspected they were dealing with the same murderer in both cases, especially when they realized delores dewitt was a single mom and a nurse, just like karen lofton. but first, they exhausted the usual suspects. delores had an ex-husband and an ex-girlfriend, but both had solid alibis. >> we had given them polygraph tests. they passed. we did background checks on

them. we found out where they were. and there was nothing that would lead us to say that they were involved. >> reporter: as in the lofton case, when detectives searched the dewitt's home, they found no sign of a forced entry, just an unlocked side-window. and inside the house, once again, no forensic evidence. but a different pattern. the killer had taken his victims with him. >> we don't know if they were killed inside the house and transported away, or if they were just transported away and killed elsewhere. >> reporter: the burned nissan maxima that carried the mother and daughter's bodies, didn't yield any significant clues either. the fire had destroyed everything but a tiny piece of jeans on delores' body. and, attached to the jeans, some leaves foliage experts identified as coming from a beech tree. odd, because there were no trees like that in the neighborhood. and the mystery only deepened when the autopsy results came back. >> ebony and delores were actually killed 24 hours prior to them being burned in the car.

that was another hiccup in the case, is where were these two bodies kept for a full day? >> reporter: it seemed the dewitt's killer took immense risks to get rid of the bodies. >> you're talking about taking two women out of their house and transporting them to another location and then stealing a car, putting those dead bodies in the car, driving past the house that you just stole the car from, and then parking it in a driveway of a vacant house, then setting that car on fire and walking away. >> reporter: and the autopsy also revealed that delores and ebony were strangled, not shot as the loftons had been. it was a puzzle. were they dealing with a serial killer or not? >> did you think one guy was responsible for both these crimes? >> i would go back and forth. one day i would it was all in that this is the same person. the next day, i thought it wasn't. because both crimes are so different. >> reporter: then, finally, the

detectives caught a break. they learned that a month before the dewitt murders, the owner of the stolen nissan maxima had been the victim of a break-in. she reported it, but, at the time, told police nothing had been taken. now she noticed there was -- her spare set of car keys was missing. >> so, tony, as i understand, your detective's logic goes something like this. if i can find the person who broke in, who stole the key, who then used the vehicle to transport the bodies, i'm getting close to my killer. >> exactly. it certainly would give me a direction where maybe that person then can direct me to the killer. >> reporter: 200 police officers blanketed the area and brought in more than 80 people for questioning to no avail. for many prince george's county residents like home invasion victims vicki and lloyd irvin, that meant only one thing, panic. >> it was crazy. i couldn't sleep at night. any sound. i had alarms put up throughout the entire house and plus, we got the dog, so -- >> and bars on the windows. >> yes. >> the house was turned into

fort knox. a barking crazy dog who claws at the windows if he hears a door bell ring. i mean, there was no peace in the house. and i was like, you have to turn some of that stuff down. i can't live like this because he's like, i don't care if this is going to save our life, you know? just the fear that spread was absolutely amazing. >> reporter: by july 2009, four months after the dewitt murders and six months after the lofton murders, detectives were stumped. we kept calling them and they wasn't giving us no answers, and that pissed me off because i felt we deserved something. >> the detective had made a promise to patricia that he would take down her sister's killer. would that turn out now to be an empty promise? at this point what he needed was luck, and luck was about to come his way from the most unexpected source. coming up, an unassuming

neighbor comes forward with some unbelievable information. >> at that point we realized that our investigation just took a drastic turn. >> when "dateline" continues. the calming scent of lavender by downy infusions calm. laundry isn't done until it's done with downy.

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here's what's happening in the final days of the 2020 tleks, president trump and vice president biden plan to rally in the nation's top battleground states. tonight biden and barack obama will appear together for the first time in michigan as trump heads to pennsylvania before making nine other stops. this comes as the u.s. sees its worst coronavirus case surge as hospitals struggle to keep up with the more than 500,000 americans infected in the past week alone. now back to "dateline." welcome back to "dateline," i'm craig melvin.

two double murders in one maryland neighborhood sent the community into a full-blown panic. investigators had cleared the usual suspects, and that's where both cases seemed to stall. then detectives linked a nearby break-in to one of the crimes. all roads to find that thief led them nowhere, but a big break was just around the bend. here again is dennis murphy with "the unusual suspect." >> reporter: prince george's county detectives tony schartner and bernie nelson theorized the home burglar who stole a spare key to a nissan maxima might lead them to a serial killer. but how to find him? >> we chased down all those leads, and it took us, you know, several weeks, and we came up with nothing. >> reporter: then, in july 2009, schartner got an unexpected tip. federal agents from the a.t.f, the bureau of alcohol, tobacco

and firearms, had arrested two men for selling stolen weapons. they suspected one of them had been also involved in several burglaries in the area. his name was jason scott. >> jason scott lived two, three blocks away from the dewitts' house. so obviously that's somebody that i want to go talk to. >> reporter: the detective and the thief met in a police station holding room. the subject, who was quick to deny he had anything to do with any of the burglaries, looked to schartner like a pipsqueak. >> he was a small guy. he was meek. his voice was very low. he wouldn't speak to me as you and i are speaking. he would only whisper. he would actually come up and actually whisper in my ear. >> did you think, tony, that point, "i got a suspect here"? >> no. >> reporter: a.t.f agents john cooney and dave cheplak led the federal investigation into the weapons theft, and they too were having a tough time trying to read jason scott.

>> usually we're pursuing the most violent criminals in the united states. for lack of a better word, you know, this guy wasn't a thug. >> reporter: in fact, jason turned out to be a college graduate and a valued employee at ups. >> we did a background check on him. and really, he had no criminal history. jason and his accomplice were charged with weapons theft and possession, but given that neither had a criminal record a judge released them pending trial. >> she had to basically make a decision, "all right, you're not a flight risk and you're not a danger to the community." so both were released to home monitoring. >> so they could come and go. court is telling them go and sin no more, don't be stupid, don't be a bad guy. >> yes. >> reporter: but the a.t.f agents weren't about to let jason scott walk away quite so easily. they suspected that he had oush cohp r several other co-conspirators in the weapons theft and instinct suggested he might be the type of petty criminal happy to throw others under the bus in exchange for a lenient deal. so the feds offered him what's called a proffer session. sometimes called king for a day,

or in monopoly, a get-out-of-jail free card. it's an agreement between the prosecutor and suspect that essentially says, "tell us everything you know, and we'll go easy on you." >> and the stuff that i spilled out, you will not come after me? that's the agreement? >> if we can't prove that any other way besides him telling us, then there's nothing you can do. you can't use his statements against him when that statement is given in that proffer session. >> reporter: agents cheplak and cooney had been on the job for a long time. but what happened next stunned even them. >> so we come into the room to conduct a proffer session with jason scott. myself and dave cheplak are on this side of the table. jason and his defense attorney are sitting across from us. we see that jason has three pieces of paper in front of him on the table. dave and i take a look at the papers and see about 40 different addresses. suddenly, jason admits to breaking into all these houses. not only that, nine of the houses he tells us he breaks

into, wakes people up, points guns at their heads and robs of them of their valuables. at that point, we realized that we're not just dealing with a guy selling and stealing guns. our investigation just took a drastic turn. >> reporter: jason had rocked the federal agents off their script. the king-for-a-day deal was about copping to the firearms charge and here he was telling them instead that he and his accomplice marcus hunter made a living by pointing guns at so many people's heads, including during that botched home invasion of the irvin family. >> but he's cut his deal, john. you can't go after him on those burglaries. the home invasions. >> at that point you're correct. >> he's home? he's off scot-free. >> home free. >> reporter: even better for jason, he believed his accomplice, marcus hunter alone would be left to take the fall for their crime spree. >> he figures if i'm the one who's willing to testify against marcus, that'll be his opportunity to lessen his sentence. >> smarts. cunning. how good was this guy? >> he certainly had a plan and he had an idea of what he was trying to get away with. >> it really was a real life cat

and mouse game for him. >> reporter: back at the county, detective schartner was floored when he heard from a colleague that the pipsqueak he'd interviewed and dismissed the week before, had fessed-up to a majority of the unsolved home invasions and burglaries in those well-to-do neighborhoods of prince george's county, including one his colleague had been investigating. >> and i thought, "oh, good for you. you got your case closed out. but i'm still here with four dead women that we haven't solved." and i said, "hey, just out of curiosity, can you give me that list?" >> reporter: when the detective plotted the addresses jason had pushed across the table on a map, he couldn't believe the picture that emerged. >> is this an ah-ha moment in your investigation? >> this is our ah-ha moment. this is our first break in the case. >> coming up. >> we don't know if we have our guy, but we certainly have something to investigate. >> the investigation was about to lead them here, something called the spooky house.

and a federal officer on this case would soon be spooked himself. when "dateline" continues. kim is now demonstrating her congestion. save it slimeball. i've upgraded to mucinex. we still have 12 hours to australia. mucinex lasts 12 hours, so i'm good. now move! kim, no! mucinex lasts 3x longer for 12 hours.

>> this is ground zero. this is where i responded to, was this location, and this is where the dewitts were found. >> reporter: thinking he'd made the deal of a lifetime, mild, meek jason scott had confessed to a wave of home invasions and burglaries in prince george's county, maryland. but by doing so, he had

unwittingly provided homicide investigators with the first real lead in the lofton and dewitt murder investigations. what's what happens up here as you continue to go up? what are the other dots? >> so these other various dots here along the map are the locations where jason scott admitted to breaking into the houses here on woodlawn. >> reporter: and here is what the detective found strange. jason had admitted to every unsolved burglary on the block. all but one, the house from where the nissan spare keys were stolen. >> for me, the most important part of this puzzle was to find out who broke into this house right here where the vehicle keys were stolen. >> in the interrogation, he did not give you that address. >> he did not. >> reporter: an anomaly, schartner wondered, or did jason know just how important the car keys were and deliberately keep that house off his list? >> we don't see guys that break into houses and steal a tv then morph into a serial killer. >> we don't know if we have our guy. but we certainly have now something to investigate. >> reporter: detectives schartner and nelson teamed up with atf agents cheplak and cooney to create a task force to

solve the riddle of jason scott. >> when you guys talk to friends and family, trying to figure out who he was, did anybody tell you he was a nice guy? i can't believe that you've got him in the frame for this? >> nobody had anything like that to say about him. as a matter of fact, most people knew nothing about him. he was almost a ghost. >> reporter: a ghost indeed. when investigators examined items seized at jason's home, they found this. disturbing videos he apparently shot as he snuck around the neighborhood. turns out jason scott was as scary a peeping tom as investigators had ever seen. >> video of someone walking through the woods, videotaping people through their homes in various states of dress and undress. getting ready for work or getting ready to go to bed. >> this is deeply creepy stuff. >> absolutely. >> reporter: the person who knew him best was marcus hunter, the accomplice first arrested with jason scott. but marcus wasn't talking. investigators wondered, was he afraid of jason?

another former co-conspirator was telling investigators jason was no one to cross. >> he's sensitive. you got to watch how you talk to him. >> these guys would say, "if i ever got into a fight with jason, jason, you know, wouldn't fight me back. but two weeks later, he'd be the type of guy to come back and burn my house down." >> that's the type of dude he was, he's crazy. >> reporter: three weeks after his king-for-a-day deal, jason scott was still walking the streets. investigators knew enough about him to worry for their own safety. >> his m.o. was, he would specifically go and cut the power to these homes, cut the alarm lines, so one night sleeping and i kind of become aware that all of a sudden the power is off in my house. so knowing that jason knew my name and thinking he could figure out where i lived, i actually grabbed my gun and proceeded to tactically clear my house. just to make sure that he wasn't the reason for the power being out. as i worked my way through the

house and into the kitchen, i finally come up and i notice that in the backyard the entire neighborhood is dark. at that point, i take a sigh of relief and i realize it's not him. but that's how concerned i was. he's that dangerous a guy that i recognized he needed to be in jail. >> reporter: if jason scott was smart, the task force simply had to be smarter. and investigators noticed jason didn't seem to understand an important legal nuance. his proffer didn't guarantee him complete immunity. the cops could not use his own words against him, but they could use the words of others. so when investigators found that other accomplice of jason, they grilled him. >> do you know of him to break into a house and just take car keys? >> yeah, he talked about one job, a couple of jobs he'd going in and take the keys and just have just in case he needed the car. >> reporter: these details eerily mirrored what happened in the dewitt murders.

>> he likes to steal car keys, spare keys. and he likes to come back later and get that car. >> that was exactly the case with the nissan, right? >> first check. >> he liked to park cars in vacant houses, preferably houses that were for sale. >> again, the torched car with the bodies -- >> -- was a vacant house that was for sale. >> reporter: detective nelson nailed down several connections between jason scott and the first mother-daughter murder, the loftons. most important of those, jason's car, a dark blue toyota camry. it matched the description of the mysterious car one of the lofton neighbors had seen. >> that could very well have been the vehicle that the neighbor had seen the night of the killing. >> yes. >> reporter: then, investigators discovered another sickening piece of evidence, a video jason made of the victims of one of his home invasions. a mother and her teenage daughter. >> he brought her into her bedroom and set up a video camera. and in the process of setting up that video camera, in which he was going to, basically, film himself sexually assaulting her.

that camera happened to pan right by his face and that screen shot showed us this. >> wow. >> this is what a lot of jason's victims saw. it's cold, calculating eyes, lifeless. >> reporter: investigators were shocked, even more so when they dug up the old police report and noticed what the perpetrator they now knew to be jason had blurted out to the mother and daughter just before he left. >> okay. here it is. he said he didn't want to hurt us, but he said he was supposed to kill us. >> reporter: yet all this evidence was purely circumstantial, not enough to charge, let alone convict jason of murder. but that was about to change. and it had to do with the one case police had plenty of evidence for, the weapons theft. when the agents questioned jason

about it, he mentioned the spooky house spooky house, an abandoned building somewhere off the beaten path in upper marlboro, he said, where he and his accomplices went to split up the loot. detective schartner had a spooky feeling he'd brought more than guns. >> we're still trying to find the place or house or wherever where the dewitts were stored or kept for those 20-some-odd hours. >> so the spooky house, whatever it is, could be the place? >> absolutely. >> reporter: and according to jason's proffer, if his statements led to new evidence, that evidence could be used to prosecute him. >> my first thought and impressions were that this is going be, like, a old, rickety house, maybe falling apart. >> it doesn't feel like we're heading to spooky house, guys. >> and it wasn't until we came here that we realized there was a long driveway here that maybe made sense. >> there it is, huh? >> reporter: the spooky house was a georgian mansion, up for sale, and like the property where the nissan was set on fire, vacant.

>> what a hideaway to do whatever you want to do away from prying eyes, huh? >> absolutely. and at night, this is absolutely pitch dark. this is just a playground that jason scott had. >> reporter: the task force called in the forensic team. >> we walked down here through these rocks here, and that's when i first initially saw the sweater, which was actually right down here in the rocks. >> reporter: it was the charred remains of a blue sweater, the kind ebony dewitt had worn the last time she'd been seen alive. >> and once we saw that, we said, "hey, this is it. this is finally something." and you're talking about a high five moment? we looked a bit further, and walked down these rocks here, and then scattered within these leaves over here were, were the jean pieces. >> reporter: jeans that seemed to match the jean fragments recovered from delores dewitt's body. leaves covered the ground and the task force wondered whether they were beech tree leaves, the type that were found attached to delores's jeans.

detective schartner brought an expert to the spooky house to identify the foliage. >> and he pulled up here, and he said, "this is the jackpot of beech trees." >> poor ebony and her mom were here. no question. >> without a doubt. >> reporter: but to arrest jason, investigators needed so they hit him again linting jason is talking, and if you don't, you'll be the one to take the fall. >> that did it. marcus hunter finally agreed to cooperate. right away he dropped a bombshell about jason. >> the specter of him becoming a monster grows with each and every stone we overturn. >> coming up. >> i think he truly thought he could outsmart us. >> could he? what would it take to put jason scott behind bars. when "dateline" continues. way. with so many changes, do you know if your plan is still the right fit? way.

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almost six weeks after jason scott walked out of the prosecutor's office with a potential stay out of jail deal in hand, they persuaded his am dock police to cooperate. the king for a day was about to be dethroned. >> marcus says about a month twier to the dewitt's being killed, he and jason are running through the back yards.

jason stops and looks into the house and notices ebony and he starts to stare at her. marcus gets uncomfortable and says, hey, we can't stay here all night. you need to go. >> much more damaging, the accomplice told the task force that after yet another robbery and approximately an hour before delores and ebony were killed he'd given jason a ride to his car, parked just a block or so from the dewitts. and the accomplice had more. >> he said there was at one point and it was during the time that the loftons were murdered that he had seen jason scott for a short time frame with a glock 17. >> a glock 17. the very weapon used to murder karen and karissa. >> i had one of our investigators try to find out who purchased glock 17s over the last two years and then contact those people and find out if they can account for their handgun. and he found out that a home was

broken into 13 days before the loftons were killed and during that break-in their glock 17 handgun was stolen. >> and here is where detective nelson got lucky. the state of maryland requires handguns to be test-fired before they're sold so it can archive each gun's shell casings to help identify or trace the weapon should it be later used in a crime. >> we immediately took out the shell casings and had them compared to that known shell casing from that known handgun. and during that testing they were able to verify that all six shell casings came from that one particular glock 17. that was the weapon that was used to kill both of my victims. >> once we found out where the murder weapon came from that was used to kill loftonsm we needed to find out if jason scott ever had that gun in his hands. so we asked his accomplice marcus hunter if they ever broke

into a house in this one particular neighborhood. he said they did, it was only one house. we never told him which one it was. and he took us directly to it. the house that the glock was stolen from that killed the loftons. as far as that handgun goes, i think that was the nail in jason's coffin. we know he stole that weapon. >> did that solve the lofton murders? >> it got as close as we were going to get. >> detective schartner and nelson arrested jason scott at his home on september 2nd, 2009. >> i distinctly remember telling him, jason, take a look at your house, this is the last time you will see it. >> he didn't have a response. he just gave some type of noise, smacking his lips as if i'll be back. >> i think he truly thought he could outsmart us. and fortunately between bernie and i and the two agents from the atf we outsmarted him. >> and personally the takedown of jason scott made the

detective a promise keeper. >> he said i'm going to get him. if it's the last thing i do. he said i'm going to get him. and he got him. >> in exchange for his cooperation marcus hunter got a reduced seven-year sentence for weapons possession. it would be another three years before the atf and county police analyzed all the evidence against jason scott. when all was said and done, he was sentenced to 185 years in prison. >> one of the things that the judge said, and i'll never forget this, is he said you're not even a crime wave here, tsunami of crime. >> satisfaction to take down a guy like this? >> extreme. >> it's the proudest moment in my career. >> but jason did cut one final deal. in exchange for acknowledging that prosecutors had enough evidence to convict him for the dewitt murders, the state agreed not to prosecute him for the loftons. that didn't sit well with the lofton family but it was the best investigators thought they

could do. >> but the bottom line is we know that jason is gone forever. he only has one life to give. we can't punish him any more than what he's already being punished. >> the serial killer, the master robber and burglar, will likely die behind bars. the neighborhoods he terrorized are safe again. but under some roofs there's been damage to that concept of home as a sanctuary. take vicky and lloyd irvin. they've kept their burglar bars, their home alarm system. they didn't know how much they needed that stuff until we filled them in. >> let me tell you something that will probably freak you out and this comes from guy number two in your house. he said after the home invasion, they came back. >> are you serious? >> he wanted another round. they parked in front of your place, did a little surveillance, scoped it out, and jason scott wanted to come back in and even the score. >> i didn't know that. that's scary. >> could have been your picture on the 11:00 news. >> that's right. how does one person cause so

much damage and so much hurt and so much loss to so many people? it still blows my mind. >> that's all nor this edition of "dateline." i'm craig melvin. thank you for watching. first up on msnbc, three days to go with the election closing in. both candidates are crisscrossing the country. >> today president trump is making four stops in pennsylvania as biden stumps in michigan where he'll take the stage not once, but twice before president barack obama. our nbc news correspondents are on the ground. early voting numbers shattering records. more than 80 million votes have already been cast and that number may reach befor