but first, long island's serial killer. >> that's how we know that we're dealing with a monster. a hannibal lecter. >> mysterious murders. and murders. >> four of the victims were found in a burlap-type material. >> kaj larsen traces the trail of a serial killer still on the loose. this is babylon, long island, an hour's drive away from manhattan, and it is known for beautiful million dollar homes and secluded beaches. but that same isolation that people come here to seek, as of late, has been masking a darker element. in december, police in long island make a shocking discovery. >> i don't think it's a coincidence that four bodies ended up in this area. >> for the past couple of years, women kept disappearing on long island. now, police think they may know why. >> we could have a serial killer. >> we are dealing with a psychotic murderer. >> police still don't have answers, so we tried to get to the bottom of this eerie mystery. >> where do we go now, gus? >> gus coletti, a man neighbors call the unofficial mayor of this community, shows me around. >> that's the house. that's where it all began. >> reporter: he tells me about a night last may that brought an unbelievable mystery to his doorstep. >> she showed up at my door. and she was banging on the door screaming "help me, help me, help me." i opened the door and she stepped in. and she just stood there yelling "help me." he later learned the woman was 23-year-old shannon gilbert. >> i picked the phone up and started to call 911 and she bolted out the door. a car was coming down the road, slowing, stopping, slowing stopped and i asked what they were doing. he said they had a party and she got upset and left. he was looking to find her to bring her back to the party and he took after her. >> in the car? >> in the car. and that was the last time i saw her. >> reporter: coletti says he waited 45 minutes for the police. by the time they arrived, shannon gilbert had vanished. when police came back later, they questioned the driver would took off after her. the driver told him he brought shannon from the city out to long island. police also questioned the man who was throwing the party that shannon attended. that was joseph brewer, who did not return our phone calls to speak with us about this story. police told coletti gilbert wasn't just a party guest at brewer's house. >> brewer's the one that hired this young lady to come out here. >> shannon gilbert was an escort who posted ads on craigslist. because of her work as an escort, shannon's sisters often worried about her. why did you guys come all the way down here? >> because my sister disappeared. >> when did you first know that your sister had gone missing? >> we first found out that sunday. her boyfriend called me and said that she hadn't come home in two days. >> did you have any thoughts then? >> honestly, you know, i just thought maybe she found some friends, partied for two days and then she was going to come home. but then when we looked through her sprint account and figured her last calls were to 911, it kind of changed our whole perspective of what became of her. >> reporter: shannon's phone records showed she was on the phone with police for 23 long minutes before she showed up at coletti's door for help. >> they didn't feel that they were being taken seriously or being helped and they were very distraught. >> reporter: gilbert's family started working with dottie laster and a a team of private investigators to find shannon. laster and her team have been digging into the case for months. they're especially concerned about that 911 call. >> she was in danger. she has not come back. she has not called anyone. >> reporter: so what did you do? >> we pretty much from there tried to do our own investigation, made up flyers, went door to door. ashley found a piece of her jewelry. >> reporter: in searching near brewer's house, they say they turned up something police had overlooked. >> the police had been there and searched it before the sisters went there, but when the sisters went, they said they found her earring on the front porch. so now they're more frantic. now they're more frustrated. >> reporter: they got even more frustrated when they were left without suspects. >> i feel sorry for them. >> reporter: police ruled brewer and the driver out as suspects. so the family began working with investigators to piece together any clues from her life before she disappeared. >> this is actually shannon's signature. >> reporter: we went back to visit shannon's sister sara in the economically depressed region of upstate new york where they grew up. her sister says right before she disappeared, shannon was trying to get out of escort work. >> she was taking online classes, trying to stray away but it's hard. we all grew up below poverty, you know? >> she liked to dress up, she liked to have a good time, she liked to party. >> yes. >> was she like that in high school too? >> no. she was very quiet. she was like the bookworm. >> reporter: this is shannon gilbert's middle school. she started in the eighth grade production of "annie" here. and like so many small town girl, heed dreams of bright lights and big cities, but what she found was that the reality when she got there is it wasn't nearly as glamorous as she envisioned. when she couldn't pay the rent, she found work with an escort agency. easy money paid the bills, but ultimately made her life harder. after only a short time as an escort, her family says she had an arrest record and a drug habit. i've watched and you guys are very close. were you close like shannon like that as well? >> yeah, we were close. if one of us went missing, i'm sure my sister now would do the same thing we're doing to try to find her. >> the family kept urging the please search, to please take the dogs and it was about to get cold. >> reporter: when police finally took search dogs out to look for shannon gilbert months after she disappeared, they made a shocking discovery. >> missing persons unit called us out on saturday to follow up on an investigation on a missing person. i saw the skeletal remains of a body. >> reporter: over the next couple of days, police would find three more sets of remains. coming up, the search for shannon and the chilling possibility that a serial killer is on the loose. but nothing's helped me beat my back pain. then i tried this. it's salonpas. this is the relief i've been looking for. salonpas has 2 powerful pain fighting ingredients that work for up to 12 hours. and my pharmacist told me it's the only otc pain patch approved for sale using the same rigorous clinical testing that's required for prescription pain medications. proven. powerful. safe. salonpas. i don't always have time to eat like i should. that's why i like glucerna shakes. they have slowly digestible carbs to help minimize blood sugar spikes, which can help lower a1c. 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[oinking] [hissing] [ding] announcer: cook foods to the right temperature using a food thermometer. 3,000 americans will die from food poisoning this year. check your steps at foodsafety.gov. this past december, police out searching for shannon gilbert in the area where she disappeared in long island stumble on not one, but four badly decomposed bodies. >> okay, good morning, everybody. >> reporter: police commissioner richard dormer delivers news that terrifies shannon gilbert's family. >> i don't think it's a coincidence that four bodies ended up in this area. we could have a serial killer. >> reporter: four of the victims were found in a burlap-like material. that indicates two things. one, that it's very likely that those four victims were killed by the same person -- a serial killer. and the second thing it suggests is that the killer most likely killed his victims elsewhere and transported them here to be dumped. in january, police put names to the remains. shannon's family is relieved. she's not one of them. but they're still alarmed. all four victims are eerily similar to shannon in age, height and looks, and every single one advertised on craigslist as escorts. had police searched far enough? one of the bodies police identified was amber lynn costello. her sister, kim overstreet, is looking for answers. >> i was doing research, trying to backtrack and getting everything i could. and, you know, it got to the point where i was obsessed with it. >> reporter: overstreet says police have told her very little about the investigation, so like the gilbert family, she started doing her own digging. >> it's my baby sister, you know. it eats at me every day. it consumed me. >> reporter: kim herself used to work for an escort agency. she tried to teach her sister how to stay safe on the job. >> i worked for the service and the guy had to have a home phone listed in his name. if there was no home phone listed in his name you didn't go. >> reporter: but she said her sister was a drug addict which made her even more vulnerable. so where we going now? >> we're going to where amber was staying, where the last place she walked out of was, where she met the guy that picked her up. >> reporter: this is the house where amber was last seen. on the night that amber disappeared, kim was out of the state. are you okay? >> yeah. it's just hard. >> reporter: tell me what's going on. >> it's just this was the last place she was. you know, and i've been here so many times with her and i just can't believe the one time i'm not with her, it happens. that morning she had got a call from a guy who was willing to set up a call for late their night. he called her again maybe 10 or 5 after and said he was coming down the road for her to go ahead and walk out. she hung the phone up, gave the phone to the people that she was with and said if my sister calls, tell her i love her. she walked out the door, was never seen again. >> reporter: families and friends of the other victims tell similar stories. each apparently disappeared after meeting clients. melissa bartholomew's family may have even gotten a call from the killer. just days after she went missing, melissa's baby sister picked up the call because she thought it was her sister. >> at that point it was five days when the first call came in and, you know, caller i.d. and melissa, she answers, she's all excited and there's a guy on the other end. >> reporter: the family got six separate calls from someone using melissa's phone. police don't want the details out there, but melissa's mother lynn will say the caller was threatening and wouldn't answer the family's questions. >> we didn't know what he did to her, if she was still alive, he wouldn't say if he wanted money or -- >> reporter: on that final call, lynn says he confessed. >> he did confirm that he killed her. so that's why we were thinking that this guy obviously held these girls and tortured them. because why else would he have called for over a month unless he was just torturing us? >> reporter: the family attorney, steve cohen. >> that's how we know that we're dealing with a monster, a hannibal lecter, someone who's very bright and very calculating and very patient. >> reporter: in april, police find the remains of up to six more victims. they speculate about something truly horrifying. there may be more than one serial killer at work here. >> certainly the medical examiner is going to be looking at the possibility that shannon gilbert is one of the remains. >> there is no secret that we've been dumping bodies out here for decades. >> reporter: lou colombo is a retired officer from long island. he shows us how hard it is to search here. >> you can just take a look at it and know you literally cannot walk in from the roadway into this area. you know, and as a result, it lends itself to discarding a body, making it almost impossible to find. >> reporter: he says police have always known the area as a good place to get rid of a body, and he explains why this will be a tough case to crack. in all fairness to nassau county, the suffolk county police department, there aren't really any hard and fast clues here, right? >> nothing. there's no physical evidence of forensics unlike you'd find at a conventional crime scene, at an apartment or at a home. >> reporter: shannon gilbert was not among the remains police found. it's been over a year since she disappeared. as the families of the victims gather to remember their loved ones, none are any closer to knowing what happened. >> we're hopeful because she wasn't recovered so that does give us the hope that she still might be out there but at the same time, it's just -- we want that closure, we want to know. >> we are dealing with a psychotic murderer who is very bright, very deliberate, very calm, very well prepared, who will kill again. next on "cnn presents" -- >> was the bullying part of the reason you think, erica, that your best friend killed herself? >> most definitely. there's no question about it. >> what led this 13-year-old to the brink? >> we have no evidence that bullying or harassment took place in any of those cases. and later, what it takes to fight the multi-billion dollar illegal animal trade. a monkey refuge where the people live in cages and animals roam free. over the south pacific in 1943. vietnam, 1967. i got mine in iraq, 2003. u.s.a.a. auto insurance is often handed down from generation to generation, because it offers a superior level of protection and because u.s.a.a.'s commitment to serve the military, veterans, and their families is without equal. begin your legacy. get an auto insurance quote. u.s.a.a. we know what it means to serve. excuse me? 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[ major nutrition ] new ensure high protein. ensure! nutrition in charge! >> this is samantha's swimsuit and it's been hanging here, and i just can't put it away. >> a swimsuit hanging lifeless since november 2009 when michelle johnson's only daughter took her own life. >> to see your child lay there lifeless and not know why. >> reporter: what she would learn is that her 13-year-old's world had become unbearable. >> we believe that she was just hiding from everybody because she was feeling helpless. samantha was kind of a tomboy and she was perceived as gay. >> was she gay? >> no. we don't think she was gay. she was 13. >> reporter: samantha was the first of seven students to commit suicide in a single minnesota school district in less than two years. parents and friends tell us four of those teens were either gay, perceived to be gay, or questioning their sexuality, and at least two of them were bullied over it. we're about 30 minutes outside of minneapolis in anoka-hennepin. this is the biggest school district in the entire state, but the reason we're here is because it has become a battleground over homosexuality in the classroom. the district has a controversial curriculum policy that says staff must remain neutral on matters of sexual orientation. it's ignited a culture war, one that's playing out in school board meetings. >> the homosexual lifestyle is a social controversial issue that should be addressed in the home and not the schools. >> these children are human beings. we're allowing these kids to be treated as second class citizens. >> reporter: allegations of bullying have brought unwanted media attention, and cnn has learned a federal investigation to this quiet suburban community. >> a student threw me up against a wall, lockers, and screamed "fag" at me. >> reporter: mike thurston, an eighth grader at anoka middle school isn't gay, but he's the president of his school's day/straight alliance. >> a student, for whatever reason, came up to me during social studies said to me so how big was it in your mouth last night? >> reporter: the bullying made school a daily battle for kids like mike and samantha. erica hoops was samantha's best friend. >> yeah. she didn't feel safe anywhere. during volleyball they would call her names like fag and be like go over to the boy's locker room. you shouldn't be in here. >> did any adults see this? >> yeah, but they didn't ever do anything. i was in the locker room at one point when she was getting harassed, and the coach was looking at it first. but she didn't stop it anyway. >> reporter: samantha's mother, michelle, didn't learn about the bullying until she showed up one day at volleyball practice. >> and the coach said, can i help you? and i said, i'm samantha jones' mother. and where is she? she said, oh, i haven't seen samantha in weeks. and i thought, what? how can that be? she's taking the late bus home. so she said, well, i know that there's a couple of girls that are being very mean to her. >> so the coach knew she was being bullied. >> right. >> had she ever told you that before you came down to practice? >> no. >> did you see anyone bullying samantha? >> reporter: the district requires staff to report all bullying. we reached out to samantha's coach. >> there was issues everywhere in her life and her situation, and they were addressed to the best of the ability, and i just -- i don't have anything else to say. >> reporter: samantha never made it to another volleyball practice. just like justin auberg didn't make it to his 16th birthday. justin was gay. >> and this one girl told the whole school. >> reporter: his friend brandi says the bullying began shortly after justin was outed in the eighth grade. >> he told me somebody had like grabbed his balls and said, you like that" and eventually his counselor noticed something was wrong and she ran up behind -- >> reporter: justin's mother, tammy auberg, says she was never contacted about the incident. and then just months before taking his life -- >> he came to me and said, mom, a kid at school said i was going to go to hell because i'm gay. >> can you say without a doubt that justin's suicide was connected to the bullying? >> yes, i believe it was connected. do i know what the last thing was that happened that made him make the final act? no, i don't know what it was. >> reporter: we will never know what drove sam