am trying a case, what drives me the most is the victims that i wanted to speak for them. i wanted to speak for helene. >> i just turned on the news. woman found murdered in denver, colorado. i just grabbed my son and screamed and cried. >> was it someone she worked with at the radio station, could it be the boyfriend that she just broke up with in december marks >> you are giving the detectives names of people? >> yes, we looked at everything. i was even like, where was ted bundy at that time? >> we have to look at every stone, every bubble. hundreds, thousands. >> she is driven. her tenacity is just remarkable. >> i knew i was going to find him. it was a competition between he and i. >> your heart is pounding like, oh my god, this is real. >> i said, i found him, i know who killed helene. hello and welcome to "dateline." helene brezinski lived by a simple philosophy, smile and make the best of everything. the budding journalist did just that as she started a internship in college radio. then, helene was murdered. this led detectives into the darkest corners of the criminal world before a ground breaking investigative tool helped to bring the secret to life. here is josh mankiewicz with "a promise to helene. " 40 years is a long time. that is 40 winters here in colorado, and countless snowfalls. it was on a day like this that a young woman disappeared. her name was helene, and helene had a friend named kimberly, a friend who kept her word. >> do you have any idea how many years you were signing up for when you made that promise? >> no. >> for those nearly 4 decades, kimberly latourette kept her promise. 40 years looking at faces, 40 years meeting with detectives, 40 years retracing helene's steps. >> when i make a promise and make a commitment, i follow through. >> helene never knew it, but she had another friend . >> you never met helene . do you feel like you know her? >> i do. i feel like i know her as well as i possibly could. >> shannon was 3 years old when helene disappeared and it was not until 2019 that she accepted a challenge. >> i wanted to win for helene. helene brezinski grew up as the baby daughter in a close-knit family of five in hamilton, massachusetts . >> everybody that met her like her company. >> janet was her older sister by nine years. >> that you did not treat her as like this annoying younger sibling? you guys were pretty tight? >> we were. she was my best buddy. she was a surprise, i think, to the family. she just brought sunshine in life to our household. >> i met her my freshman year of high school. she was a sophomore. we both were a part of a singing group called harmony. that is really where i got to know helene very well. >> she loved to sing ? >> yes, she loved to perform. >> i'm involved with harmony, musical group at regional. >> helene spoke about her school out for a classmate's local radio show. >> my philosophy in life, yeah, i have one. you should just be yourself and make the best of everything. smile. yeah, that is what i do all the time. >> here she is, smiling along with kimberly in their musical group. also joining in, kimberly's older brother, john. >> it was a real feeling of camaraderie, but also a dedication to excellence in our singing. >> he remembers the date camaraderie turned to something else. >> we started talking, and for me, it was an immediate spark. it was that fluttery feeling you have when you know you are talking to somebody that you realize you really like, immediately. >> they were just that in love. they were each other's first loves in high school, but very genuine. >> it did not last beyond high school, but john and kimberly both kept in touch with helene after graduation. helene attended wheaton college in massachusetts, where she sang in another group, the whea- tones. there she is in the back row with a black dress on. one more thing, as much as she loved her singing, helene had another passion, journalism . >> what you think would happen to her, where was she had it? >> to great things. i saw helene the christmas december of 1979 at church. she told me that she was going off to denver to do this internship to further her interests in journalism and she was very excited about it. >> helene arrived in january 1980 to begin that internship at a radio station in denver , a long way from home. fortunately, she had some relatives nearby. >> your family didn't worry about her going off to colorado, because she was not going to be alone and she was staying with your aunt and uncle? >> exactly. >> then, came that day, january 16th. helene had barely been there two weeks when she grabbed the bus from the radio station around 6:00 p.m. to go back to her aunt and uncles house . she had made the commute before without a problem. that night, helene pruszynski never made it home. >> my parents called me and said, they had just gotten a call from my aunt and uncle, this was maybe 10:00 at night. >> what did you think had happened? >> we had no idea. this was so unlike helene, something had to be wrong. >> the next morning, the news, none of it good, made its way back to massachusetts. >> that was the first thing that came up, hamilton woman found murdered in denver, colorado, and from there it was just horror and chaos. >> i went crazy. my son was 16 months old. i just grabbed my son and screamed, and cried, and i just couldn't believe it was happening, not to helene. >> that moment would launch a 40 year waste quest for justice to find helene's killer, and to learn what happened on that wintry night. >> detectives, family, and friends desperate for clues grasp at straws. who would want to harm helene? coming up. >> she gets off the bus and then she just disappears? >> she just disappeared. >> was the summer she worked with at the radio station? could it be the boyfriend she just broke up with in december? >> i thought i would be a suspect, actually. >> when "dateline" continues. when you see what it's really like when our skin touches wool... you see why we need downy free and gentle with no perfumes or dyes. it not only makes your clothes softer, it is gentle on your skin. it breathes life into your laundry. a slow network is no network for business. that's why more i choose comcast business. and now, we're introducing ultimate speed for business —our fastest plans yet. we're up to 12 times faster than verizon, at&t, and t-mobile. and existing customers could even get up to triple the speeds... at no additional cost. it's ultimate speed for ultimate business. don't miss out on our fastest speed plans yet! switch to comcast business and get started for $49.99 a month. plus, ask how to get up to an $800 prepaid card. call today! ♪ ♪ [ speaking minionese ] no. no. no. no. no. no. [ gasps ] [ chuckling ] good job, junior. way to go. [ chuckling ] [ speaking minionese ] in helene pruszynski's mall, massachusetts town of her family and friends sat stunned. she had been found murdered in a snowy feel in colorado. >> she was my first love, so she had a very special place in my heart. and what happened to her was so devastating. >> her wake was just horribly sad. i mean, no one could even speak. what could you say? >> you just go through the motions, and when it is all over, you sit and you still say, i can't believe this happened. >> murder changes everything. >> oh, it does. >> it changed the mood in rural douglas county, colorado. a high profile murder case will do that. >> as snow began to fall in the field of where young helene pruszynski was found, -- >> back in 1980, tony spurlock was a young deputy sheriff in colorado. today, he is the sheriff. >> what was douglas like then? >> douglas county was a completely rural community between colorado springs and denver. >> not a lot of homicides back then? >> maybe once every four years. >> investigators determined helene was last seen alive getting off that bus from work. >> from the bus driver me we know she got off that bus. from there-- >> nobody got off with her? she did not have trouble on the bus? >> there was no indication from witnesses she was in any distress or anyone was following her. >> she gets off the bus and then she just disappears? >> she just disappeared. >> helene's body was found the next day in a field nearly nine miles from that bus stop. she had been stabbed nine times. an autopsy revealed she was also rape. >> what did you learn from the body, the scene, the autopsy? >> a number of her clothes were missing. she was wearing a midsize winter jacket for colorado at that time and a scarf she was lying on her back. she had no defensive wounds, but she had wounds on her knees and lower leg area, which would tell us that she had either crawled on her knees at some point into that rough area of the grass, based upon her injuries. >> and she did not have defensive wounds me suggesting she was not fighting her attacker? she was trying to go along with him me maybe getting her to let her go to mark >> let some of us to believe that it was not a stranger, it must be somebody that she knew. >> but she did not know anybody there, did she? >> she did not know anybody, but she was working at a radio station. could it be somebody she turned down for a date or a ride or something that got angry? >> helene's friend, kimberly, started thinking about the man in helene's life. they were mostly just friends, but she passed their names to investigators anyway. >> you are giving the detectives names of people and saying, you need to check out this guy, this guy, this guy? >> yes. we said, could it be the boyfriend that she just broke up with in december? could it be-- i looked at my brother, i said, john, could it be you? >> of course, john was helene's ex-boyfriend veered as john worked through his own grief, it occurred to him, police might come knocking. >> i thought they would. i thought i would be a suspect, actually, but they never contacted me. >> that is because investigators quickly determined john was in massachusetts when the murder happened. in colorado, investigators focused on what little evidence they had. >> different world for law enforcement bagman. no surveillance cameras, no license plate readers, none of that. >> this was during the age of law enforcement where we still did not have dna. there was no technology that would help us track where she was at. >> there old-school police work did turn up something. a witness had seen a young man with medium build in his 20s or 30s, 5'9" or 5'10", he was standing by a car on the side of the road. it wasn't much. investigators wanted more from the witness. >> investigators put that person under hypnosis, and used a sketch artist to draw a rendition of the person that she saw standing next to a car on daniels park road, which would have been 100 yards or so away from where the body was found. >> networks, putting somebody under hypnosis? >> here's the thing, i've been doing this business for 40 years and i have heard where it worked and when he did not work. >> the result was this sketch. was it the killer, and would it lead anywhere? coming up. >> they are known as serial killers. according to law enforcement officials, there are at least 35 of them roaming the country now. >> a chilling new possibility. >> i was even like, where was ted bundy at that time? was he in colorado? >> a string of notorious killers on the loose. could one of them have committed this crime? >> these prolific serial killers certainly fit. >> it certainly fits. >> when "dateline" continues. but hey...nothing wrong with sticking it to the boss. ooooh, flo, you gonna take that? why would that concern me? because you're...the... aren't you the..? huh...we never actually discussed hierarchy. ok, why don't we just stick to letting dave know how much he can save when he bundles his home or auto with his boat or rv. wait, i thought jamie was the boss. [ laughter ] it's funny because i'm not boss material! nexgard® plus helps you protect your dog from fleas, ticks, heartworm disease, and more... all in one delicious, monthly, soft chew. use with caution in dogs with a history of seizures or neurologic disorders. nexgard® plus: the one you want for one-and-done protection. in the weeks after helene pruszynski's murder , police at last had a possible image of their suspect, except, it was not leading them any closer to her killer. >> you start throwing that sketch around and no one knows who it is. >> exactly. no one came forward and said, i know who that guy is. >> months went by and detectives just hit a dead end. >> it was clear that they had exhausted all of the leads by the wintertime of 1980 me going into ' 81, the case had gone cold. >> for the victim's family, there may be no greater frustration that having a loved one's case go cold. often, someone needs to play the role of the tireless advocate. even at only 26, kimberly realized that and made her promise. which was-- >> i saw helene's parents and i just promised them that i would not stop for as long as i was living, and doing everything in my power to find helene's killer. >> everything to kimberly meant constantly calling detectives, generating press coverage, anything to keep a laser focus on the case. >> i did not want to see her parents, or her sister, or her brother have to not only deal with just day-to-day living, take some of that burden off of them and for them to feel good that somebody was still actively working on it, and keeping that case alive. >> and then, in 1983, the case did seem to gain new life. throughout the 70s and early 80s, a number of serial killers had been grabbing headlines. >> we looked at every serial killer. i was even like, where was ted bundy at that time was he in colorado? we looked at every known serial killer that was active at that time to see if they could have possibly been in colorado. >> and then, there were these two men, henry lee lucas and oddest tool here they were drifters, rested and jailed in the early 80s and began telling law enforcement something astonishing, how they had killed more than 200 women in a dizzying spring across the country. >> prime analyst there have painstakingly recorded hundreds of dress, out of trouble, and method of killing in the lucas tool murder cases. >> that is murphy dennis reporting another pair for nbc nightly news. >> they are known as serial killers, and according to officials, there are at least 35 of them roaming the country now. >> and these two told police about one particular victim in colorado. >> they confessed to committing the murder of helene pruszynski. what was unique about them was that detectives often thought that there might have been another person may be in the car, waiting for whoever they took out into the field. that was one of the theories. >> so, these two guys that work together, these prolific serial killers, that certainly fit? >> it certainly fit. >> it's pretty seductive when a couple of serial killers were on the hook for a lot of other murders confessed in your murder, because it would close a lot of cases if you can link them to these guys. >> right. obviously, this is awesome. we got a confession. >> colorado investigators headed to texas to interview lucas themselves. the detectives showed him a map and asked him to pinpoint where he and tool picked up helene. >> and we took her way out in the country, well, there's a bunch of rocks and stuff out there. she was stabbed to death, raped, covered up with a sheet , and some plywood. >> then, lucas added another detail. >> she was stabbed to death, and shot once i think in the head. >> who shot her? >> i shot her in the head. >> at that moment, they had a problem, helene was stabbed, not shots. to detectives, this confession was starting to sound phony. they dug deeper, looking into lucas and tool's long trail of arrest records. >> we could link them to other jurisdictions by other legal documents that could be authenticated, but it would be impossible for them to be in two places at one time. >> they were not in colorado at the time helene was killed? >> they were not in colorado at the time she was killed. >> i was about to confess to a murder they did not commit? what would be in it for them? >> they were becoming famous and they knew they would spend the rest of their lives in prison, if not on death row. >> so why not be the most prolific serial killers in the country? >> exactly. >> as for any other serial killers on the prowl back then, none could be placed in colorado at the time. ted bundy actually had spent time there in the late 70s, but he was behind bars in florida at the time of helene's murder . the serial killer leaves had dried up. >> was that disappointing when that did not pan out? >> that was disappointing. we knew at that point we were back at .0 with nothing to work on. >> it would not happen quickly, but over time, this case would go from .0, to 100 with a young detective up for a challenge. coming up-- >> what i focus on when i'm working a case, what drives me the most is the victims. i want to speak for them. >> a new investigator at a bold , new approach. >> you are talking about hundreds of names here. >> hundreds, thousands. having been a competitive athlete most of my life, i think really it was a competition between him and i. i knew i would find him. i wanted to win for helene. >> when "dateline" continues. and it began her family's touching story that is still going on today. vicki: childhood cancer, it's just hard. stacey passed on christmas day of 1986. there is no pain like losing a child, but saint jude gave us more years to love on her each day. marlo thomas: you can join the battle to save lives. for just $19 a month, you'll help us continue the lifesaving research and treatment these kids need now and in the future. jessica: i remember as a child, walking the halls of saint jude, and watching my sister fight for her life. we never imagined that we would come back. and then my son charlie was diagnosed with ewing's sarcoma. vicki: i'm thinking, we already had a catastrophic disease in our family. not my grandson too. marlo thomas: st. jude has helped push the overall childhood cancer survival rate from 20% when it opened to 80% today. join with your credit or debit card for only $19 a month, and we'll send you this saint jude t-shirt that you can proudly wear to show your support. jessica: for anybody that would give, the money is going towards research, and you are the reason my child is here today. charlie: i was declared-- this will be two years cancer free. but there's thousands and thousands of kids who need help. saint jude, how many lives they do save is just so many. marlo thomas: charlie's progress warms my heart, but memories of little angels like stacy are why we need your help. please become a saint jude partner in hope right now. [music playing] welcome back to "dateline." i'm andrea canning. helene pruszynski was found murdered outside of denver. police pursued everything, including two false confessions from two nestorius notorious serial killers. decades would pass before a young detective picked up the case and set her sights on a promising new suspect. back to josh mankiewicz with "a promise to helene." helene pruszynski's murder had become the textbook example of a cold case. in 1948, a ray of hope sprang up . it came from a somewhat newer textbook. the use of dna evidence had become a revolutionary tool in criminal investigations. douglas county detectives realized, there was dna from their suspect in evidence. >> there was body fluids on these pieces of materials or swabs from the autopsy that had not been tested. so, we were very excited at that time, because we had an abundance of dna evidence available to us. >> evidence that had been preserved, even though you are not testing for dna back then, no one was. >> know. and to this day, i give the credit to the karo color