>> 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 kindof on the edge of my seat. >> he truly thought he could outsmart us. >> reporter: i'm lester holt, and this is "dateline." 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 ar 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 his wife vicki and their son, just 4 years-old at the time, are still haunted by the image of the gun men. 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 i

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

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♪ >> prince gorgeouses county detectives ther rises the burgh lar might lead them to a serial killer, but how to find them. >> we chased down all of those leads and it took us several weeks and we came up with nothing. >> then, in july 2009 federal agents from the atf had arrested two men for selling stolen

weapons. they suspected one of them had also been involved in several burglaries with the area, his name was jason scott. >> jason scott lived two or three blocks away. obviously that is somebody i want to go and talk to. >> the detective and the thief met in a police station holding room. he denied he had anything to do with it looked like a pip-squeak. >> he was a small guy, his voice was very low. he wouldn't speak to me as you and i would speak. he would whisper in my ear. >> did yyou think i got a suspet here? >> no. >> they led the investigation into the weapons theft. they were having a tough time trying to read jason scott. >> pursuing the most violent

criminals in the united states. this guy wasn't a thug. >> in fact jason turned out to be a college graduate and a valued employee at ups. >> he had no criminal history. >> jason and his accomplice were charged with weapons theft and possession. but a judge released them pending trial. >> you are not a flight risk or a danger to community and both were released to home monitoring. >> court is telling them don't be stupid. don't be a bad guy? >> yes. >> but the atf agents were not about to let jason scott walk away so easily. they suspected he had other conspirators and he might be the type of petty criminal willing to throw others under the bus. the feds offered him a proper session. it is known as a get out of jail

free card. an agreement between the prosecutor and suspect saying you tell us everything you know and we will go easy on you. >> the stuff i spilled out, that is the agreement? >> if we can't prove that besides him telling us, you can't use the statement against him. >> the agents had been on the job for a long time, but what happened next stunned even them. >> so we come into the room to conduct the proper session with jason scott. we are on this side of the table. jason and his defense attorney are sitting across from us. jason has three pieces of paper in front of him. we see about 40 addresses. jason admits to breaking into all of these houses and nine of them he breaks into, wakes people up, points guns at their heads and robs them of their valuables. we realize we are not just

dealing with a guy selling and stealing guns, our investigation took a drastic turn. >> the king for a day deal is about copping to the firearms charge and he is telling him he and marcus hunter made a living by pointing guns at so many peoples heads, including the botched home invasion of the urban family. >> you can't go after him. >> that point, you are correct. >> home free. >> even better for jason, he believed his accomplice, marcus hunter alone, would be left to take the fall for the crime spree. >> if i am the one willing to testify against marcus, that is his opportunity to lessen his sentence. >> how good was this guy? >> he had a plan and an idea of what he was trying to get away with. >> it was a real life cat and mouse game.

>> the detective was floored when he heard from the colleague that the pip-squeak he interviewed confessed with the burgh -- burglary. >> you got your case closed out but i am here with four dead women we have not solved. just out of curiosity, can you give me that list. >> when the detective plotted the addresses jason pushed across the table on to the map he couldn't believe the pictures that emerged. >> is this the ah-ha moment? >> it is. this is our first break in the case. >> coming up -- >> we don't know if we have our guy, but we certainly now have something to investigate. >> the investigation was about to lead them here. something called the spooky house. a federal officer on this case would soon be spooked himself.

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by doing so he provided homicide investigators with the first

real lead. >> what happens here as you continue to go up? >> along the map are the locations where jason scott admitted to breaking into the house. >> here is what the detective found strange. jason admitted to every unsolved burglary on the block. but the one where the nissan spare keys were stolen. >> the most important part is to find out who broke into. >> we don't see guys that break into houses and then morph into a serial killer. we don't know if we have our guy but we now have something to investigate. >> the detectives teamed up with atf agents 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? >> nobody had anything like that to say about him. he was almost a ghost. >> 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 of a peeping tom as investigators had ever seen. >> video of someone walking through the woods videotaping people in their homes, getting ready for work or ready to go to bed. >> creepy stuff. >> absolutely. >> the person that knew him best was marcus hunter. but marcus was not talking. investigators were wondering if he was afraid of jason.

another co-conspirator was telling investigators jason was nobody to cross. >> if i ever got into a fight with jason he wouldn't fight me back but two weeks later he would come back to burn my house down. >> three weeks after his king for a day deal jason scott was walking the streets and investigators knew enough about him to worry for their own safety. >> he would specifically go and cut the power to these homes. one night sleeping and become aware the power is off in my house. >> so, knowing that jason knew my name and thinking he could figure out where i lived i grabbed my gun and i proceeded to tactically clear my house to make sure he was not 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. i take a sigh of relief and think it is not him. but he is that dangerous of a guy where i recognized he needed to be in jail. >> if jason scott was smart, the task force simply had to be smarter. investigators noticed jason did not understand an important legal nuance not guaranteeing him complete immunity. the cops couldn't use his own words against him but they could use the words of others. when they found the accomplice of jason, they grilled him. >> a couple of jobs he just have them. >> these details 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. he liked to park cars in vacant houses or friendly houses that were for sale. >> detective nelson nailed down several connections. most important of those jason's car, a dark blue toyota camry matching the description of one of the mysterious cars one of the neighbors has seen. and then investigators discovered another sickening piece of evidence. a video jason made of the victims of one of his home invasions, a mother and one of her teenage daughters. he set up a video camera. the camera happened to pan by his face and the screen shot

showed us this. >> wow. >> this is what a lot of the victims saw. cold, calculating eyes. lifeless. >> investigators were shocked, even more so when they dug up the old police report and noticed what he blurted out to the mother and daughter just before he left. >> he said he didn't want to hurt us but he was supposed to kill us. >> yet all of this evidence was purely circsubstantial. >> it had to do with the weapons theft. when the atf agents talked to jason about it, he mentioned the spooky house. some kind of an abandoned old property off the beaten path where he and his accomplices

used to go to diffey vy up the . >> we are trying to find the place or the house where they were stored or kept for the 20 hours. >> the spooky house, whatever it is, could be the place. >> absolutely. >> if the statements led to new evidence, the evidence could be used to prosecute. >> my thoughts would be like this is an old house, falling apart. it wasn't until we came here that we realized there was a long drive way here that maybe main sense. >> there it is. >> it was a georgia mansion up for sale, like the property where the nissan was set on fire, vacant.

>> what a hideaway. >> absolutely. at night this is absolutely pitch dark. this is a playground that jason scott had. >> the task force called in the forensic team. >> walk down through the rocks and that is when i saw the sweater in the rocks. >> it was the charred remains of a blue sweater. the kind that she has been wearing the last time she was seen alive. >> this is it. we looked at it further and walked down the rocks here and scattered within these over here were the jeans. >> jeans that seemed to match the fragments covered from the body. the task force wondered whether they were the types of leaves attached to the jeans.

an expert was brought in to identify the foiliage. >> they eliminated his accomplice as a murder suspect and hit him up again, jason is talking and if you don't you will be the one to take the fall. marcus hunter finally agreed to cooperate and dropped a bombshell about jason. >> him becoming a monster grows with each and every stone we overturn. >> coming up -- >> i think he thought he could outsmart us. >> could he? what would it take to put jason scott behind bars. and one more chilling revelation for the irving family. >> are you serious?

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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 that sparked marcus hunter to cooperate. the king for the day was about to be dethroned. >> marcus tells us about a month prior to the dewitts being killed he and jason are running

through the backyard because they had just done the job. he notices ebony and starts to stare. marcus gets uncomfortable saying we can't stay here all night. you need to go. >> much more, the accomplice told the task force after another robbery and almost before that an hour he had given a ride and the accomplice had more. >> he said at one point, it was during the time that the loftons were murdered that he had seen jason scott for a short time with a glock 17. >> the very weapon used to murder karen and charissa. >> i had one of the investigators try to find out

who purchased glock 17s and contact those people asking if they can account for their handguns. a home was broken into 13 days before the loftons were killed and during that break-in their glock 17 handgun was stolen. >> the state of maryland requires handguns to be test fired before they are sold to help identify or trace the weapon should it later be used in a crime. >> we took out the shell casings and had it compared. during that testing they were able to verify that all six came from the glock 17. >> once we found out where it came from we could find out if

jason scott ever had the gun in his hands. we asked if they ever broke into a house in this particular neighborhood. he said they did. he took us directly to it. the house the glock was stolen from. >> as far as the handgun goes, that was the nail in jason's coffin. we know he stole the weapon. >> did it solve the murders? >> it got us close as we were going to get. >> jason scott was arrested at his home. >> i remember telling him jason, take a look at your house. this is the last time you will see it. >> he just gave some type of noise as an i'll be back. >> i think he truly thought he could outsmart us. between bernie and i and the two

agents from the atf we outsmarted him. >> personally the take down of jason scott made the detective a promise keeper. >> i am go to get him if that is the last thing that i do. he got him. >> in exchange for his cooperation, marcus hunter got a reduced seven-year sentence for a weapons possession. another three years before the atf and county police analyzed all of the evidence against jason scott. he was sentenced to 185 years in prison. >> the judge said you are not even a crime wave, you are a tsunami of crime. >> but jason cut a final day. in exchange for acknowledging prosecutors had enough evidence to convict him for the dewitt murders, the state agreed not to

prosecute him for the loftons. they had their doubts about whether all of the evidence really proved he had pulled the trigger. >> we wanted a trial in this case because we wanted to see him on the stand admit what he did and be charged and convicted and sentenced for murder. >> what do you say to someone that wants to have their day in court against this guy? >> i understand his position and the lofton family. i feel for them. i want them to have their day in court. i typed up a statement of charges but i couldn't get the blessing from the states attorneys office to go forward. >> you would say jason scott is the killer? >> he is who took charissa away from them. we know jason is gone forever.

he only has one life to give. we can't punish him anymore than he is already being punished. >> the serial killer, master robber and burglar will likely die behind bars. the neighborhoods he terrorized are safe again but there has been damage to the concept of home as a sanctuary. take vicky and lloyd, they kept their burglar bars and home alarm system. they didn't know how much they needed that stuff until we filled them in. >> 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 surveillance. scoped it out. jason scott wanted to come back in and even the score. >> i didn't know that. >> could have been your picture. >> how does one person cause so much hurt and damage and loss to so many people?

it blows my mind. >> that's all for now. i am lester holt. thanks for joining us. right now. a developing story in the south bay. police investigating a double homicide after two people were found i right now at 11:00, a developing story in the south bay. police investigating a double homicide after two people were found dead inside a home. i'm peggy bunker. >> and i'm terry mcsweeney. a neighborhood in shock after the discovery. we were first to break the story on our twitter account and 5:00 newscast. it was in the evergreen neighborhood. and marianne favro joins us with the latest. >> reporter: police are still out here processing the crime scene. you can see, this is