finally have achieved her life long ambition to care for people and make them well. >> she pops in my head and i just think how sad because she would have been one heck of a nurse. that is all for this edition of "dateline." i'm natalie morales, thank you for watching. >> i'm craig melvin. >> and i'm natalie morales. >> and this is "dateline." >> during the middle of the night, i heard this loud noise. it sounded like someone was in the house. i opened up her door to her bedroom and i thought, i'm hearing things. >> your instincts were right, that something happened in the middle of the night. >> do you think your child is safe in your home sleeping. >> she was just 16. emma, the honor student. cheerleader and volunteer.

>> she could get along with anybody. >> always so kind-hearted and sweet. >> she wanted to be a nurse and she had a plan. >> she went to sleep one sunday night and never woke up. >> i saw a 16-year-old female laying in her bed. there was a bullet hole in the wall. >> so she's been shot? >> someone had fired a shot from outside of the residence. >> was emma a target? that weekend she'd seen a moistureus figure in black. >> she was in fear. >> she was shaking. >> now two brave friends set out on a secret mission, could they help catch her killer. >> you're trying to bring down a murder suspect. >> i knew it was something that had to be done. >> it all became a lot more real. >> hello and welcome to

dateline. emma walker was a spirited teenager with a knack for stirring up fun. pretty and smart, she had her whole life ahead of her. but after her death detectives faced a tough investigation. whoever shot emma had been brazen and it would take a bold plan to catch her killer. here is andrea canning with "noises in the night." >> when the autumn chill seeps into this community north of knoxville, tennessee. hundreds of high school students are dprarawn to the blaze of fry night lights to cheer on their home town heroes, the bobcats. she was the friday night light who perhaps shown brightest of them all. emma walker. a bobcat cheerleader since sher freshman year at central high. >> she was a really good cheerleader. some of them would just go through the motions but emma would put her own kind of

sparkle into what she would do. >> fellow cheerleaders kelsey and lauren say their friend could be sassy, too. >> and she said i am kind a big deal. >> and i take it she said that with a hint of sarcasm. >> yes. >> people who didn't know her, they were like oh, she's super pretty cheerleader. oh, no. but then they would meet her and be she's the nicest person i ever met. >> her long time school friends. >> once you got to know her. wow, she's a down to earth person and really sweet. >> she had a smile that could light up the room. a big, beautiful smile. >> emma's parents jill and mark say that infectious smile was the hallmark of her playful personality. >> she likes to play jokes on me. grabbing my iphone, and taking selfies of herself.

i have no idea. >> emma volunteered at an animal shelter. at school she was an honor role student with a clear career goal. >> she wanted to be a neonatal nurse and when we talked about the different professions and get to the ones about babies and she's like that is what i want to do. >> it is no surprise that emma got noticed by boys at school and there was one boy she definitely noticed back. >> that is really all she talked about at first, was just he's super cute. >> he was reilly gaul. two years older than emma, popular, too. a standout wide receiver on the bobcats football team. >> do you think reilly would make it to the nfl. >> if it was anybody that would do it, it was reilly. >> alex and noah say he wasn't just a high school jock. he was active at church and loved "star wars" movies. >> he's a nerdy guy and that is how we met and later into high school he got more into

football. but he kept with his nerd roots. >> he was really funny and i think that is why emma fell for him in the first place. because they were both super goofy. >> she had a big crush on him. >> she did. >> there was just one problem. reilly already had a girlfriend. but he said he broke up with her to date emma. >> and things got serious pretty quickly between the two of them. >> yeah. >> but as the months went by, it became clear reilly, the star football player, was also, well, a player. it turned out his ex wasn't really an ex after all. >> and he had like promised his ex-girlfriend that he would take her to prom that year. and take emma, his senior year. >> she was okay with this? >> she wasn't okay with it but she did let it happen. >> she couldn't let go? >> no. >> that must be hard for a parent when you see a guy who has got two girls on the go. that is not cool. >> no. it is not cool. and she was young and had a mind

of her own and didn't want us to voice our opinion about our concerns. >> emma's determination to be with reilly caused a lot of tension between her and her parents. >> how does it work when your trying to be good parents and your daughter has that strong personality? >> it is difficult. >> very difficult. >> i mean, she just was very stubborn and thought her way was the right way. she wanted to learn for herself. >> emma and reilly dated on and off in high school for two years. when reilly graduated and went off to college, half an hour away, they tried to keep the relationship going. but just before thanksgiving in reilly's freshman year, emma saw snapchats of reilly with other girls on campus and she broke up with him for good. emma's parents say the tension at home evaporated. >> it must have felt so good to be the happy family again. >> it did. our whole household was different. >> the household wasn't calm for

very long. on november 20th, 2016, a sunday, emma went for ice cream with her dad and planned to get up early for school the next morning. >> i told her good night, love you. i'm going to bed. and during the middle of the night, i heard this loud noise. >> what kind of noise was it? >> it sounded like someone was in the house and opened a door and slammed it. and then i heard it again. >> mark jumped out of bed to check on emma and her brother. >> i opened up her door to her bedroom, and i stared her for probably 15, 20 seconds and she was just lying asleep in her bed. and i shut the door and went to my son's bedroom and he was in the bed asleep. so i thought, i'm hearing things. so i checked the doors around the house and went back to bed. >> in the morning, emma's mom jill woke up early.

>> and i went in to wake her up and i couldn't wake her up. >> what is going through your mind in that moment? >> i had no idea. and i can't recall a lot of it. i just know i checked for a pulse. >> and there was no pulse? >> no pulse. so, you know -- >> emma's young brother evan rushed in. >> i wish he never had to experience it. it was like a nightmare. >> jill called 911. >> i just tried to wake up my daughter for school and she has no pulse. >> you said she's nonresponsive. >> yes. >> what happened to emma walker? >> coming up, the investigation begins. >> i saw a 16-year-old female laying in her bed with a small amount of blood on her pillow. >> people thought she might have

overdosed on something. >> they thought she had ingested poison or whatever. >> it is a mystery right now. >> it is all a mystery. >> when "dateline" continues. broken windshield... take 1... hey guys, my windshield just got broken, i feel like i need to blow off some steam. let's go... 1, 2, 3, 4... mr. blanks? there's no need to be stressed. geico makes it easy to file a claim online, on the app, or over the phone. yeah, but what if i never hear back? that's gonna make me want to go jab...jab! nope! your geico claims team is always there for you. that makes me want to celebrate with some fireworks. 5,6,7 go... boom, boom, boom, boom boom boom boom boom boom, yeah! geico. great service without all the drama. our most advanced formularonamel repair. helps you brush in vital minerals to actively repair and strengthen enamel.

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horrible had happened to emma was tearing through town. friends calling friends. >> just bawling. and i was like you need to breathe and calm down and what is wrong and she said emma is dead. and i said what is happening. because it didn't register in my mind, on our end. >> it didn't seem real at first to nathan either. >> i was like, yeah, that is my best friend but no, she didn't pass away. it just hit me and i started bawling. >> emma's ex boyfriend riley was at his dorm when his phone was flooded with calls and texts. he grieved on social media. >> how much she doesn't deserve this. she's in a better place now. tell god about our bible verse. >> and did heart goes out to riley, he's lot -- >> a lot of people had commented i'm so sorry. >> prayers for you. >> still, no one knew yet how

emma died. >> what are some of the rumors that are now floating around on social media about what happens to emma? >> people had thought she might have overdosed on something. >> some people said brain bleed. >> the biggest one were people that didn't know her were look saying that she killed herself. >> was there any part of you that was confused and thinking well maybe it is possible. >> no. >> no part of me thought that emma would ever take her life. >> this is a mystery right now as to what happened. emma is there and you know that she's not survived whatever has happened but you don't know what. >> it's all a mystery. >> investigators arrived with just sketchy details from first responders. >> they thought that originally that it was a suicide, that she had ingested something, poison or whatever. >> knox county major mike mcclain was adesigned to the

case with alan merit. >> i saw a feel with a small amount of blood on her pillow and some people confused that she had gotten sick or hadd -- had ingested something and caused her to vomit. >> when he looked closer, he saw something unusual. >> there was a hole in the wall next to emma's bed. a bullet hole. and while ome a little blood was visible on emma's pillow. when investigators inspected her head they saw a small entry wound. >> so she's been shot. >> yes, ma'am. >> shot in her own bed. >> the bullet struck her just left and above the ear, basically it was a fatal wound. >> she had to have been shot then through the wall. >> it was obvious that someone had shot from outside of the residence into the residence striking her in the head. >> this is not the kind of neighborhood that has drive-by

shootings, right. >> yes, ma'am, that is correct. it is actually a fair low crime rate area. >> as the detectives processed what was now a crime scene, they found more clues as to what might have happened. >> we go outside of the residence and that is where we also determined that there was a second shot that had been fired through the end wall of the house. >> so bullet holes in two separate walls. and there in the walker's yard. >> we find a shell casing, a spent casing that had been fired and then as we again work around to the end wall of the residence, we found a spent casing and a live round. >> when emma's parents learned what had happened, they were barely able to take it in. >> they had told us that she had been shot. it's unthinkable. >> emma's father mark recalled with horror the noises he heard during the night. >> knowing that those noises that i heard were gunshots and

they sounded nothing like gunshots. >> but you're instincts were right, that something happened in the middle of the night. >> you think your child is safe in your house sleeping. >> but who would want to kill this sweet, popular girl whose goal isn life was to care for newborn babies. it turned out the last few days of emma walker's life had been anything but normal and might be the key to unraveling the mystery. >> coming up -- >> she sees a person dressed all in black -- >> a mysterious figure at emma's door. >> and then this person comes to the front door and starts trying to get in the house, turning the doorknob and beating on the door. she's in fear and panic. >> i would have been terrified. >> when "dateline" continues. n y gel... available over the counter. voltaren is powerful arthritis pain relief in a gel.

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emma walker was shot dead if her own bed. at 16 years old, she had her whole life ahead of her. >> yeah, all of the great things that she would have done. >> yeah. i mean proms and graduations and things that we never get to see. getting married, having kids. >> as em yu's family began to imagine life without her, police were focused on finding her killer. they were talking to her family and friends about the days right before the shooting.

>> this is a lot of activity in the period of two days that is unexplained. >> it was the weekend before thanksgiving. friday night, emma and her group were celebrating a football win at a friend's house. her friend zack was at the party when emma received a text message from an unknown number. it said something about riley. he had been taken. >> her text messages saying someone has riley. >> someone has riley? >> yeah. someone has kidnapped him. >> riley kidnapped? the strange messages kept coming. and then her phone rang. riley is in the line. >> he was screaming, help me, emma, i need your help. >> you could hear riley calling for help. >> yes. emma and her friends rushed out of the house and there was riley. >> and he had his hands on his head and looked confused. i could see her yelling at him what is going on and she was really angry. >> emma was furious with riley. she and her friends thought the

whole thing was some kind of prank. >> we all said, it is very farfetched for him to be kidnapped. we didn't think twice about it. >> but if the kidnapping was a joke, what happened the next morning was no laughing matter. emma's friends told police that saturday she drove herself home from her friend's house. >> as she's pulling in the sub division approaching her residence she sees a person dressed all in black and as she gets closer he cinched the hood up and put some sunglasses on. >> she was texting her friends a play-by-play. >> as she gets in the resident then this person comes to the front door and trying to get into the house. turning the doorknob and beating on the door. she's in a fear, she's in a panic. so she reaches out to the one person that she thinks could help her, when ch was riley gaul. >> emma had just broken up with riley and was angry at him for what she thought was the strange

kidnapping stunt the night before. still she texted him this. i hate you. but i need you right now. she facetime called him and asked him to come over. >> why do you think she reached out to him given that they have just broken up. >> i think he was a sense of security for her. he was a protector from other things. >> riley searched the house and neighborhood but saw no signs of anyone. neither called the police. but now dektectives discovered surveillance footage from a neighbor's house and there he was. >> that is the mysterious man in black. >> it was. >> were you able to see a face? >> no. >> a possible intruder, an attempted kpaping. what was going on? police needs to talk to riley right away. they asked him for detailed about the kidnapping and he insisted that it really

happened. >> it was traumatizing. i didn't know what could make of it. i went to my step-dad's house and this van pulls across in the -- and these two guys were driving across the street and one of them grabs my bag and the other one is around the corner and they just, like, put their hand over my face and took me to a van or whatever. >> why did they do that to you? >> i genuinely have no idea. they did ask me, they were like, they were like, who do you want to talk to for the last time and i started freaking out and i said emma. and they made me call emma and i was just crying saying that she thought it was a joke. she thought i was playing a prank on her. >> emma didn't buy the kidnapping story but she was terrified when she called him the next day about the man in

black. >> she facetime called me and she was crying and i said i'll come down and check it out. >> that is the only person that they think of would want to hurt emma. >> the only person at her house on saturday morning, that is the first thing i thought of. >> riley told police even though they were broken up, he still cared for her. in fact, they spoke on the phone sunday night in the hours before emma was shot. >> i just told her how much i loved her and that i was sorry that she didn't want what we had any more. she said she didn't care about the relationship any more. and she cared about me and she loved me but didn't care to be with me any more. >> he spent the rest of the night on campus about 25 miles away crying over the breakup. >> i sat in the parking lot just looking at pictures of us. >> he woke up to people texting and calling with their condolences. >> so i was like, what are you talking?

i said, no what are you talking about? >> riley, the heartbroken ex, and now he's lost the love of his life for good. but this pair of seasoned investigators had their radar up. >> as you start seeing more of his personality, you could see that he had to have her. >> coming up, a closer look at that mysterious man in black. >> she had actually seen the man in black. she recognized him by build, by his gait, the way he walked and carried himself. >> who was he? when "dateline" continues. telind in california. my parents' job is to look after them. and it's my job to test the product. the best almonds make the best almondmilk. blue diamond almond breeze. special guest flo challenges the hand models to show off the ease of comparing rates with progressive's home quote explorer. international hand model jon-jon gets personal. your wayward pinky is grotesque.

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good afternoon. >> i'm cory coffin. at this hour, bipartisan lawmakers with history today. the republican-led senate echoed the house vote to overturn president trump's veto of multi-billion dollars in military funding. first and likely only veto of his presidency. meanwhile just 17 hours into the new year more than 1600 more americans have died of covid-19.

as florida and california health official announce have new cases of the highly contagious covid strain in the u.s. now back to dateline. welcome back to dateline, i'm natalie morales. who shot emma walker. the day before she died a menacing man dressed in black triggered a panicked call to her ex boyfriend riley gall. by the time he got there the man was gone. now detectives were about to discover something riley didn't tell them. and it would send the investigation into overdrive. once again, here is andrea canning with "noises in the night." >> emma walker had been murdered and all over twitter riley gaul was the grieving ex. >> what did he change the bio

to. >> rest easy my angel, i love you so much. >> and now emma's friends were looking back on her romance with riley. and they remembered a high school boyfriend who was jealous, possessive, even obsessed. >> he started to get very kind of controlling of her. like where she was, what she did. if she wanted to hang out with her friends, she was like you're not going. >> he didn't want her to hang out with people, like it was just him and her. >> and if emma went somewhere without him. >> he would text her 40 to 100 times. he's just blowing her phone up. emma, emma, emma, talk to me, text me back and call me. >> he would call her 20, 30 times. >> emma's parents thought the relationship was toxic. they had seen their daughter change. >> this new personality with riley in the picture was not one that you recognized? >> no. not with emma. her fun-loving self was very

closed off, more in her room. >> angry. >> angry at us. >> was it kind of like her spark had been extinguished? >> yes. >> her parents said riley seemed intent on driving a wedge between emma and her family. >> he would tell her she didn't really have parents. that she barely had a brother and i think he just wanted her to think that that was -- he was all she had. >> this is a nightmare situation for a parent. >> yes. >> jill and mark had always been involved parents. monitoring their kids' social media and cell phones and they even have a tracker on emma's car. so when things got bad with riley, they tried to limit emma's contact with him. but he always seemed to find a way around their rules. >> he would show up to our church because they couldn't tell him to leave or a basketball game because it is a public event going on so they can't tell him he shouldn't be there. >> and when emma finally broke up with him a few weeks before

she died, even his close friends said it seemed like he was unraveling. >> were you worried about him? >> yeah, very. >> i think this is when we started to see if he wanted to do something, like, he could. >> he seemed a little unstable to you. >> yeah. >> and now that emma was dead, her friends weren't buying his sad messages on social media. >> what are you thinking when you read riley's post. >> he's trying to cover up for himself. >> did you think he did it? or something else? >> i thought he had something to do with it. >> police were thinking the same thing as they listened to stories about emma and riley. >> based on my experiences as a detective, it was a abusive relationship. not physically, but more of a psychological and emotional type of abuse. >> police were skeptical of everything riley said. they didn't believe the kidnapping story. and when they talked to one of

emma's friends in the neighborhood, they were even more suspicious. the friend was certain riley was the mysterious man in black. >> she had actually seen the man in black and believed it to be riley and she recognized him by his build, by his gait, the way he walk and carried himself. >> so during that interview, police were closely watching i'lly. they noted how he referred to emma in the strangest way. >> the girl, she texted me. >> which girl? >> the one that passed away. >> oh, okay. what is her name. >> emma. >> this is someone he's professed his love to and gone on social media and spoke out about how she's his everything and all that, but yet when he goes to talk to me in the interview, he referred to her as the girl. >> how did you get from there -- >> as the interview progressed, they tried to nail down his whereabouts the night emma was shot. he stuck to the same story, he

was at college in maryville, tennessee, almost half an hour away crying in his car over the breakup. >> i remember getting back in my dorm at 4:30 and my buddy asked why i was getting in so late. >> as police questioned riley, they became more and more skeptical and he was picking up on it. >> i hope to god i'm not a suspect in her death. >> did i say you were? >> i hospitpe you don't think i >> it was an over top reply. it was phony. >> i'll hurt myself before i hurt her and that is what i've done. >> did you shoot into emma's house? >> no, sir. >> riley was now the prime suspect. but they had let him go. they didn't have enough evidence. and there was a missing piece to the puzzle. where was the gun that killed emma. it would take two young men on a dangerous mission to find it. >> riley gaul is about to become the target of a secret

operation. >> coming up -- >> he set up a listening device in the car. >> and the police could hear you but you couldn't hear them. >> yeah. >> could these two friends find that missing gun and the killer. >> this potentially could be very dangerous. >> absolutely. you're going to have two boys if a car with a guy that is believed to have already killed one person with a murder weapon and this is a huge dangerous thing. >> when "dateline" continues. introducing a revolution in the world of pain relief:

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the day before emma walker was killed, riley gaul's grandfather called police about a handgun he owned. >> he filed a report that the gun is stolen. >> that missing gun was a problem for riley, too. he lived with his grandpa. and the gun was the same caliber as the one used to kill emma. police didn't think that was a qa coincidence. >> did he express that he knew where the gun was or did he completely deny? >> he completely denied everything relevant to the gun. >> and after his denials to police, riley reaped out to his close friends alex and noah since his breakup with emmy, riley had been leaning on them for support. >> what did he say about how he felt about it. >> he was torn up throughout this whole time. i tried to spend as money time with him as i could. just be there for him whenever he needed. >> riley confided in alex and

noah again. he said he would never hurt emma. had nothing to do with the shooting, but he did have his grandpa's gun. >> they're going to find a way to put this on me. if they find the gun. could you just help me get rid of this. >> the boys were willing to comfort riley but not help get rid of evidence in a murder investigation. instead, they called lieutenant merit. >> it is amazing that they called. >> oh, absolutely. >> this is a big piece of the puzzle. >> absolutely. absolutely. like it very well just went on living their lives and minding their business. >> riley told his friends he planned to go to the bluffs high above the tennessee river and toss the gun into the water. police hatched a plan, a bold and risky sting operation. have alex and noah go with riley and the moment they see the gun signal detectives who would swoop in and make an arrest. >> this potentially could be very dangerous? >> absolutely. you're going to have two boys in a car with a guy that is

believed to have killed one person with the murder weapon. this is a huge, dangerous thing. >> dangerous, for sure. and then detectives made it even more complicated. they decided to secretly record the whole thing. >> they set up a listening device in the car itself, my car. i had inside of the jacket which sucks because i couldn't take off the jacket the whole time. >> and then you got the key fob. >> and the police could hear you but you couldn't hear them. >> yeah. >> everything came together with lightning speed. just hours after calling police. 18-year-olds alex and noah were wired up and ready to meet riley. >> and what did your parents think about this? you're very vulnerable in this position. >> my parents had just moved to north carolina. i was living on my own. i didn't have time to talk to my -- >> you did not tell your parents? >> i didn't. >> the plan hinged on the boys

texting a secret word to detectives the moment they see the gun. without tipping off riley. the pressure was intense. riley came over to noah's house. the mission was underway. >> i know that you -- >> police were nearby listening in. as instructed, the boys tried to be natural. >> i'm sorry about emma. i want to be so upset and i can't because i'm worried about getting arrested and put away for a murder that i didn't commit. never in my life would i kill someone that i loved that much. >> it sucks you have to deal with all of this. >> riley clearly had no clue about the sting. he had faith in his friends. >> i'm trusting you guys, like with my life because i mean this is 70 years in jail if i get convicted of something i didn't

do. >> why don't you just give them the gun. >> just -- it just needs to be gone. for whatever reason. it just needs to be gone. >> you guys don't have to come with me if you don't want to. if it is in the tennessee river they'll never find it. >> the boys headed out. first stop, riley's stepfather's house where he had hidden the gun. he came out holding a plastic garbage bag. detectives were still tracking the boys closely, or trying to. >> it is kind of a crazy part here. we've got detectives watching them, they leave out from step-dad's and at some point we lose them. we lose sight of the vehicle and we've lost the wire. >> that a heart-beating moment. >> yes. obviously we want to track them realtime and keep up with them. >> and police did find them again in time to see the boys make an odd detour. on the way to the river they stop for some drive-thru fast food. >> yeah, i need a cajun chicken

with two sides of hush puppies with chili and cheese on it and a large dr pepper. >> you're in the middle of this critical undercover operation and you decide to go for chili cheese fries. >> yep. >> why? >> it was almost the whole time we were like saying good-bye to one of our best friends. it was like almost comforting to kind of have it be like it was before. >> they got to the bluffs around 11:00 and pulled into an apartment complex parking lot. alex knew the security code for the gate. he used to make deliveries there. and then the big moment. the hidden camera didn't catch it. but alex and noah will never forget it. riley pulled the gun out of the bag. >> oh, my god. >> noah texted the detectives. they were supposed to pounce.

but 30 seconds passed, then a minute. no police. alex saw their suv outside of the gate. what was the delay? two minutes, still no police. the tension unbearable. then alex did something audacious. he took the gun out of riley's hand. >> is this a real gun. >> alex, why did you take the gun from riley? >> that's kind of a bold. >> it really was. >> i was watched in the backseat and i was like -- no. >> it is a instinct you'll thing and he grabbed it back out of my hands. that was scary. >> and that is when police got through the gate and made their move. >> everybody put their hands out of the vehicle now. >> riley was cuffed and taken away. the gun was still in the car. >> just pull that back. >> just to see the serial

number. >> the mission was a success. alex and noah were safe. >> riley was charged with the murder of emma walker and taken to jail. it was the end of a long crazy day. a popular football hero was behind bars. how did it all come to this? >> he was controlling and obsessive but you never thought a murder. >> and in a case already full of surprises, the biggest one was still to come. >> coming up -- a sudden change in riley's story and it is a stunner. >> as frightening and as bizarre as it is, his hope that he -- >> riley is saying i'm not a cold blooded killer. >> would the jury believe it? when "dateline" continues. when "dateline" continues. rst sign,

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almost a year and a half passed since emma walker was shot and killed through her bedroom. her exploded not guilty first-degree murder. knox county district attorney general prepared for a high profile trial. why do you think this case captured so much attention? >> people can relate to being a teenage couple in love. people can re late to breakups

and one thing that scared people in our community is emma was asleep in her own home in her own bed. >> was it stressful as the trial approached? >> yes, just the worries of what the turnout will be. >> prosecutors kevin allen and molly martin would have to prove to a jury that it was riley who pulled the trigger. >> what was your strategy going into this trial? >> i think the main thing we needed to focus on in the beginning is putting him there that night. i think the cell phone records and gps locations were very important up until that moment. >> they placed him around emma 's house. >> he placed himself in marchville and the phone records placed him in knoxville. >> so he clearly told a lie. >> yes. >> the picture we painted was a deceiver, somebody that was

phony that you couldn't get the truth out of him if you tried. >> on the first day of trial, wesley stone up ended the state's case with an unexpected admission. r rilye was there and did fire the gun but it was not murder. >> that was a fairly stunning claim. >> from the gallery, veteran crime reporter jamie saw jaws drop. >> what he said was that riley never intended to kill her and in fact, assumed he would not kill her if he shot through a wall. >> we'll ask you to find mr. gaul guilty of reckless homicide. >> not premeditated murderer. >> right. in tennessee that's two to four years in the penitentiary. >> that would be a huge different. >> yes. >> all of the state's preparation went out the window. >> the case went from who done it to state of mind. >> the defense said riley wasn't

a crazy killer, just crazy in love with emma with a bizarre plan to win her back. >> when riley gaul fired that shot in the backyard as crazy as it is and bizarre as it is, he was hoping that he could come to her rescue. >> the defense told the jury riley only meant to scar emma with the gunshots and with emma needing comfort, he'd swoop in and be her knight in shining armor. riley had no idea the bullets would pass through the house. >> some of us who know about firearms may very well know that if you shoot a into a house it will go through the wall. some of us may not. i submit to you riley gaul did not. >> the defense denied riley was the ban in black but the kidnapping story was a stunt to get emma's attention.

riley's attorney said it showed how desperate his client was to be with her. >> what riley was trying to do is get an opportunity to see emma. that's all he was trying to do. >> that would later become a theme of his defense that rather than killing emma what he intended to do was play her rescuer. >> it almost does sound like he was trying to scare her when you first hear it. >> i would think the same thing and then i went out to the scene and looked at the house and looked at where he would be standing and it is what five feet away from the house, i think the measurements were and it's me pointing a gun right at you right now and pulling the trigger. it was that close. >> so close prosecutors said it was obvious that riley was shooting to kill. >> shoot up into the air. shoot in through the window but where you shot. >> the state agreed with the defense on one point. riley was desperate to be with emma, but that desperation had

become dangerous. prosecutors argued, of course, he was the man in black. after that the kid snapping stunt failed, they said riley gave up on winning her back and instead sneaked inside her backyard and stood outside the window and fired into the wall knowing kpexactly where she sle on the other side. >> i think this is a case of reven revenge. he sought to get back at her for the hurt he perceived she was purposely putting on him for breaking up with him. >> after he killed her, the prosecutors said he went to great lengths to cover his tracks. >> and he's going to through the gun off the bluff. >> yes, sir. >> they showed the jury the video of that undercover sting and how riley tried to manipulate his closest friends into covering up his crime. >> i'm trusting you guys like with my life. >> his plan was to get away with this. his plan was never to be caught. >> which theory would the jury

believe? a reckless act or premeditated murder? they went off to deliberate and came back four hours later. >> in count one, charging the defendant with first-degree murder, did the jury reach a verdict? >> yes, we did. >> what is your verdict? >> guilty. >> you hear guilty. what's that moment like? >> relieved. >> it a sense of relief. >> riley was sentenced to life in prison. he'll be in his 70s by the time he's eligible for parole. >> we're incredibly proud of the investigatiors and work that we're almost more proud of noah and alex. >> i mean, are they the heroes in this? >> i think they are. >> lieutenant merit, the walkers call you the heroes. what do you say to that? >> do what i had to do. >> it took a lot of guts to do what you did. >> appreciate there. >> as for emma who used to joke that she was kind of a big deal, she's actually become one.

with tributes to her all over town. there is a scholarship in her name and a dog park dedicated to the young animal lover. >> it's a fun happy place to remember her and other people to remember her. >> and here at the east tennessee children's hospital, a nicu exam room is named in her memory but emma's parents believe the best way to honor their daughter is to learn from what happened. detective merit says it is important to understand when teenage drama turns into dangerous behavior. >> i think we need to educate our young people better about relationships and what a healthy helation ship is and what is psychological abuse. emotional abuse. >> and it's what we hope someone gets out of this story is awareness. >> and know what's healthy for you. >> emma may be gone, but for those who loved her, the young

girl still sparkles. >> she would want to be out there, you know, and she'd want us to be laughing and having fun and not -- you know, you can't cry all day, that you still have to live life. >> that's all for this edition of "dateline ". i'm natalie morales. thank you for watching. i'm craig melvin. >> i'm natalie morales. >> this is "dateline." i knew she would never leave her kids in the middle of a hurricane so i always knew it wasn't going to be good. >> crystal was gone, and there were lots of reasons to worry. >> she had numerous lovers, membmen and women. >> you had the husband and boyfriend failing pollies. >> on the same day. >> the answer would have to