this is not what was supposed to happen. >> the note was under her blanket. >> i saw it sticking out and i grabbed it. >> their daughter was a runaway. >> i am frantic! because i did not know how to find her. >> they called police, they searched, and then, a jogger found a red shoe and a pool of blood. >> here they are, three people at the door. >> i just started sobbing. >> they had found her daughter, but not the boy she was with. it was if he had never existed. >> we couldn't find anything -- about. >> months went by, still no trace of lj. and then, a rookie took the case. >> how did you feel about it? that this was not gonna be your case? >> i didn't think i was capable of doing this. i cried the first few hours. >> a teen found dead. >> we still don't have an answer. >> a mysterious answer and the missing suspect. >> they say, lj has killed someone before. >> and hurts to solve. >> i have the feeling, you are learning how to become a detective as you go. >> this is the case that taught me. >> you have notes, we're trying to keep your children safe. >> hello and welcome to dateline! social worker veronica made one of her toughest cases deeply personal when she decided to adopt annie. over the years, annie thrived. but it turned out, she was keeping a secret that was only discovered after her disappearance. cut a fake pregnancy really have been the motive for an all to real murder? or had any run into the wrong crowd? here's dennis murphy, with the girl with the red shoes. >> veronica kasper zach is a determined woman. >> if someone said you can't save them all. >> my mother is probably the one who would say that. but yeah i heard that a lot. >> she rarely was a. the desire to do good, to save a child was too strong. though, something in the quiet hours, she wonders if she did the right thing. >> if i didn't have that house, if i had not taken a shower. if i would have done something else, she would not have been in that situation. >> of course no one could have now and then that it would end up like this. >> police department, i need to report a one-way. my daughters missing. >> her daughter was annie grace, the when veronica first met her, she was not -- . she wasn't even her daughter. she was a client, just seven years old, with the rough childhood. >> she had been through some abuse, and she had a hard time trusting other people. >> back in 2005, veronica was a caseworker for utah's division of children services. her job was to find a home for kids who no longer had one. and he was one of those kids. >> annie has a larger than life personality. whatever she does, it is not small. if there was something she liked it, it was huge. if there was something she didn't like it, it was big. and there was nothing like it. >> drama came with it? >> oh yes. >> for a nickel tried for years to find amy a stable home. but after any had been flown back to the state nine times, veronica, young, naive, and stubborn. made the surprise decision to adopt annie. >> did your superior tell you we do not do that veronica? don't cross that line? have a professional relationship with his child but do not bring her into your home? >> that was very true and at the time i happen to be six months pregnant. so i'm sure the shot thought was the pregnant lady. she does not know what she's doing! but it was very much, are you sure? you can't save everybody. but veronica was determined to try. >> she and her then husband adopted ten year annie in january 2007. annie who had bounced around from house to house finally had a home. parents and brothers who adored her. >> she was the immediate cool big sister. she liked being the oldest, being in charge. and teaching them all this cool stuff. she was wanted, happy making memories. >> opening gifts on christmas morning, her first trip to the beach. not that everything was perfect mind you. >> there was still definitely a, i'm going to test you as much as you say you love me and are keeping me. i mean to say that i don't believe you. >> how did she challenge you? >> just the quintessential, i'm not gonna do what you say. just whatever i want. >> so psychological tussle? >> yes. >> which only intensified when annie entered her teen years. >> she was a bout as boy crazy as i could imagine. she always had a boyfriend. she liked boyfriends, they liked her. and it was never a, here let me see. i'm in love with you! this is forever! i couldn't imagine anybody being more amazing! she was very all in. >> but any was also into her education and her future. she wanted to be a therapist just like veronica. she even wanted her new family to adopt more kids. >> she's there, she's really having a hard time, i think we should bring our home. >> she was really becoming her daughter in a way. >> yeah. >> francesca ventral-y divorced and remarried. she and her new husband james settled here in utah, a suburb of salt lake city. and he had james wrapped around her finger. >> i took her with me to help me pick up her mother's valentine's day gift and a huge already crossed the right. she had away with me, she could talk me into just about anything . one of them was her favorite shoes that she found. she was so excited when they arrived. >> just a few days later, march 10th 2012, annie, now 15, was watching her brother's while veronica and james went to dinner. >> then when we came home, everything seem the same. and he had changed from running around the house in shorts to jeans. i chalked it up to, okay she's gotten cold! i had a massive headache i couldn't get rid of, and i went to take a shower, and any went downstairs to listen to music, we figured it was another saturday. >> but it was not. when veronica finished her shower, and he was gone. yay james search her bedroom. >> the note was tucked underneath her blanket. i grabbed it, and it just said i'm sorry. i have not been totally honest with you. >> annie, it turned out, was keeping a secret. in the note she wrote, i lied to my friends. i told them i was p. p? francesca and james knew that it stood for the word no teenagers parents wanted to hear. pregnant. just a few omnths earlier, they learned that any had sex for the first time. >> she had sex, so any assumed that since she had sex, i could be pregnant or i am pregnant. but the pregnancy test was negative. and she was now on birth control. so why would she lie about being p? even more alarming, is where annie said she was going. by the time you read this note, i'll be on my way to cal's love for nia, please don't try to look for me, i do not want to be found. >> the first thing is, we call the police. and the second, i called, chris. >> 14 year old chris --, annie had brought him over to the house a few times. >> he was kind of quiet, i kind of took it as the i want to make sure that you don't kill me as my girlfriends partisans. >> was he good as a boyfriend? >> his stock would rise and fall? >> she was crazy about him. >> chris told veronica he did not know where any was. but he did have some information. chris said annie told him she was running away with a guy named lj. >> we were shocked because, we didn't know all of her friends, because they changed a lot. anyone she was hanging out with at the moment. but it wasn't familiar at all. >> a police officer came and took a report. james, meanwhile, called up the gps function on any cell phone. >> it took her around the golf course. within a mile of that, which is the bridge area. >> the bridge of the jordan river. just a couple of miles from their home. a place joggers, and horseback riders were at during the day, and young lovers at night. james, veronica, and the hospital what as her phone pinged across the computer screen in realtime. >> you're watching her move? >> yes. >> it was so fast, our immediate assumption is that she's getting in the car. >> so this is a hot pursuit now? >> yeah. >> and then the signal just stopped. veronica drove to a walmart near where they tracked her phone. >> and i have her picture on myself phone and i'm showing it to the people who are sitting at the front and going have you seen this girl? >> are you collected or are you a wreak form all this is going on? >> i am, frantic! >> veronica went back home and she and james watch the front door, and they kept calling annie but her phone went straight to voice mail. >> in the best of worlds she's out with some boyfriend you may or may not know off on a lark of some kind but you can get her back in the group. >> yes our worst-case scenario is she's gonna come home. >> worst-case scenario? not even close. >> coming up! >> he had told us that lj had been by the house, threatening chris. >> and a jogger makes a grim discovery. >> 9-1-1 what is the address of the emergency? 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[coughs] when caroline has a cough, she takes robitussin. so, she can have those one on ones again. hey jim! can we talk about casual fridays? oh sure. what's up? get fast, powerful cough relief with robitussin, and find your voice. ♪robitussin♪ and find your voice. dennis murphy (voiceover): march 11, 2012, spring was still officially days away, march 11th 2012, spring was but in draper, utah, its promise was clear. still officially days away, but in utah, its promise was clear, morning to on the brush, the crisp air, the sun rising over the mountains. it should have been a beautiful day, but for a jogger on the jordan river parkway that morning, it was anything but. >> 9-1-1 what is the address of the emergency? >> you know, i'm not real sure, i'm at the river bottom, and there is pools of blood. and i'm guessing it's just an animal, but in the water right by the river there is a shoe. >> sergeant -- was one of the first on the scene. >> we called forensics, that we did a presumptive test which was able to tell us that it actually was human blood. >> human blood, that changed things. >> that made us think okay, we might have about in the, water so we called a helicopter. >> the helicopter was in the air for just under an hour before it spotted something about a mile north of where the jogger saw the blood, it was caught up in some branches. as the chopper got closer, it was clear if there was a body in the river. >> sergeant, when the divers pulled the -- what did they observe to her face? >> she had a laceration on her forehead, her face was swollen, we weren't able to tell to what extent the injuries were and we couldn't even identify who she was. >> they're jane dough, red and why plaid sure looked to be about 20 years old. her features, possibly asian. and obviously, she had been murdered. leading the investigation was a young detective named derek johnson. tell me about him. >> right when he came into the academy he sat next to me and started teasing me and the rest of the class time we just harassed each other and lofton giggled all day. jacqueline met derek at the police academy, and they hit it off immediately. >> a detective spot came open, we both applied. >> did you think rats? >> yeah. >> he caught his first case, which was also the first homicide in the small town of jaipur had seen in years. some would call police just after -- gruesome scene. by the time veronica and james saw, had been missing for nearly 20 hours. >> the information that it's an asian woman under 20 that would rule out -- >> initially we were thinking no, that is not possible, there is no way. >> but then, a detail sergeant shared with salt lake city the nbc affiliate -- there was a shoe found out the crime scene and there was one on the body. >> a red shoe, the same kind james had bought any for valentine's day just weeks earlier. veronica and james tried to stay calm. we call the police, we said hey our daughter is missing. i said logically they are going to rule it out. but they couldn't rule it out. >> after call the police, that called my parents to come and pick up our boys. i just started sobbing. >> police soon determined that 20 something asian victim was a really 15-year-old annie. she had been killed by a blunt force trauma to the head. veronica and james had thought the rapid pinging of her phone meant she was driving away, now there was no hope of her ever coming home. >> it's the worst moment of your life at that point, here they are three people at the door? >> they confirmed that it was annie. i think we were in shock. we went into automatic what do you need from us? tell us what you want, you can have, and look at anything. >> veronica told investigators which he learned from annie's on again off again boyfriend chris. and he had run away with a boy named lj. >> when you talked with lj, how did you talk to--? >> i talked to him once. >> okay. >> actually on the phone. >> okay. >> police spoke to chris and his father at their home. >> and when you talked him on the, phone did he speak with an accent? or did you notice anything distinctive about his voice? >> no. >> naturally police also had to ask chris where he was. >> i was with my grandma, and at one point i did walk up to see my friend to hang out. he was at home. >> they went through the usual questions. >> when you walk to your friends, what were you wearing? >> just regular jeans and a t-shirt and my red jacket. >> just blue jeans? >> just blue jeans, nike shoes, a t-shirt underneath, and a red hoodie on. >> do you mind if we see your nike's? >> sure. >> he wanted to help, he gave the nike's to investigators as well as this close. he even gave a dna sample. after his interview, his dad called up the sergeant. >> he told us, on his phone, call that lj, a driven by the house was threatening chris. >> so more information that this lj is a very real and threatening person. >> yes. >> detectives also spoke to chris and annie's friends spencer. he said he was at the gym with his brother the night and he was killed. >> did she have an interesting gangs? >> not that she didn't really tell me. maybe she does, because of some person named lj that i have no idea who he is. all i know she told me he was in a gang. i don't know for sure. >> before he left the interview spencer shared one more thing with police. >> she said that lj has killed someone before. she never gave me the name, but she said that she knows that or something like that. that is why she was scared when apparently lj threatened chris to come kill him. >> you thought it was your killer. >> we thought lj was involved. >> did boy crazy annie fall for a gang member -- interim police found a poem she had written to lj, and with it for the first time a name. leighton tanden. but police could not track him down. jacqueline wasn't working the case then, but she remembers crossing paths were spencer at the station. >> he immediately tensed up, clenched his fist, his eyes got big, he couldn't take his eyes off me. i thought this kid has done something wrong, he thinks i'm coming to arrest him, because i'm approaching him in uniform. >> did you share that? >> yes. you said we have received more information, now and we think we have another suspect. >> another suspect, a new name altogether. based on information from an eyewitness who may have seen annie -- the night she was killed. and knew who killed her. >> coming up. is this how annie was murdered? >> -- >> and is this the man who murdered? her? >> when dateline continues. annie -- had been brutally murdered and dumped into the jordan river. >> we kept asking, are you sure it wasn't an accident? the idea that somebody did that to her, even now it's hard to imagine that that is even possible. >> and now, police were working hard to catch her killer. >> we are trying to actively locate suspects in this case. any witnesses so that we can bring this case to a conclusion for the parents. >> and within a week of annie's murder, they found that witness. her name was joanna, and she had been picked up on a fraud charge by neighboring west jordan pd. during her interview, she started telling detectives about a young girl she had seen a week prior. the cops thought that some of which she said seemed eerily familiar to annie's case. so they called -- pd, detective came over to hear what she had to say. >> tell me what you know about this girl? >> it was the second time i've seen her over there. >> there, at the home where a man named danny used to live. >> danny -- is a guy known to law enforcement? >> yes. >> as maybe a drug dealer? >> drug dealer. he was a member of a gang called -- . and law enforcement has dealt with him quite a few times. >> danny had a long rap sheet. he had a search warrant on his home a year earlier. and now joanna was telling police she saw a girl who sounded a lot like annie, on the night and he was killed. joanna also said the girl showed up with someone the police had been searching for but could not find. >> lj, the guy annie had written that note to. the alleged gang member. the one annie had run away with. >> we had an ease entries that said lj. we had joanna telling us about lj. >> on that night, said joanna, lj and the girl disappeared into the garage. she assumed they were having sex. then, when they came out, she saw daniel approach the girl. >> he asked her if she -- and she was like no. any kind of like grabbed her head and just rounded into the wall. >> she said the girl was knocked unconscious. lj and another girl tried to calm her down. and then the three carried the girl out to the garage, and change her clothes. >> tell me about the clothes that she was transferred into? >> there was a lot of red. that's what i remember the most. >> what parts do you r