Transcript for Two missing daughters, two sets of human remains, both families seeking closure
Tonight a major break in a desperate months-long search for a missing daughter. Sparking renewed intensity for the investigation into a second disappearance. Now two families in a painful search for answers. From the one man with a disturbing history linked to both cases. Could he provide critical clues? When I found out, I showed no emotion. I was just -- shocked. Reporter: A heartbreaking mystery partially solved. But raising painful new questions in the disappearance of a Missouri woman. The last two weeks I've had a really bad heaviness in my heart. Reporter: The body of 21-year-old Jessica Runyan, who vanished seven months ago, discovered just this week outside Kansas City. Last night for me was the hardest thing I've ever done. It was hard for me to telling me began that her best friend and sister is gone. Reporter: Jessica's mother Jamie seeking solace with another grieving family, the beckfords. Ronda and Jim's daughter went missing nearly ten years ago. Two families linked together in tragedy. Both missing daughters who disappeared miles apart, both connected in one man, Kyler Yust. We've been through this before and it's a roller coaster ride of emotions. Kind of a self-presentation mechanism -- Reporter: A ring, police telling them a second skull in the same location had been discovered. I'm not going to say 100% but my gut's telling me they'll have some resolution. Reporter: The other set of remains? A potential bombshell breakthrough in the 10-year-old disappearance of CARA kapetsky. Police say it could take up to a year to get a positive identification. Both bodies found just miles away from the kopetsky home. In my heart of hearts I believe it's Kara. Everybody always said when he took Jessica, that they felt that when they found one, they would find both. Reporter: Kyler Yust, kapetsky's ex-boyfriend, allegedly the last person Jessica Runyan was seen with, denied any connection with the disappearance. Did you kill Jessica? Did you? The 28-year-old has never been charged in connection with the disappearance, authorities now investigating a homicide. The family hopeful new clues might finally link back to Kyler Yust, a man with a troubled past. Our fight begins now. We're not done. Reporter: Jessica rannian known for her easy laugh and playful spirit. We like to drive around and burglary music. Reporter: The oldest of three girls, she was a role model, her family says, to 14-year-old Megan and 6-year-old Michaela. I love you, Jessica. That's my last one of the four of us. It shows our closeness. Reporter: We first spoke with Jamie in January. She let us into their lives for her first extensive TV interview since her daughter went missing. I can talk about anything and everything about her, but it's just -- the sentimental stuff like future, past. Yeah. Sorry. Reporter: Jessica's grandfather driving us on the route he believes she took that last night. At the time still searching for clues. Jamie's pretty strong. But eventually there's a time when Jamie is -- it's going to hit her and hit her hard. Reporter: Thursday, September 8th. Jessica is at a party with friends. Six to seven people there. Sitting around, drinking beer, watching TV, goofing off. Reporter: She reportedly leaves with Kyler, a long-time friend of her boyfriend. Kyler, a man with an alleged history of violence towards women. He'd just gotten out of prison on a drug charge. She offered to give him a ride? They came together what we were told. When did you first get that sinking feeling when something was wrong? When she didn't show up at her doctor's appointment in the afternoon. Reporter: Hours later police find Jessica's black Chevy equinox, interior destroyed by fire in an isolated wooded area just off the road. There is no sign of Jessica inside. That was my worst fear that she was burnt in the car. Reporter: Early the next morning, Kyler Yust arrested, accused of setting Jessica's car on fire, charged with knowingly burning a vehicle. He's pleaded not guilty. Molly Hastings is his lawyer. Jessica Runyan's mother is essentially begging him to speak out, you've advised him not to. This is not advice to further punish or penalize Jessica's family. Kyler has not been charged with anything outside of knowingly burning this car, and that is again a charge we pled not guilty to and that we intend to fight. Reporter: Kyler still in jail waiting trial on charges relating to the burning of Jessica's SUV. In a statement to ABC news on the discovery of Jessica's remains, Hastings saying, despite developments made over the course of the past week, Mr. Yust remains charged with only one count of knowingly burning a vehicle. She continues, there are too many unknown factors to comment further, but I can assert that Kyler has not been charged with any further crimes. But there were disturbing signs in his past? Court documents show almost an escalation of violence against the women in his life. Any time we have domestic violence in a relationship, there's clearly an escalation. Reporter: 2011, an ex-girlfriend sought an order of protection against him, alleging Yust choked me and slapped me and punched me, he threatened to kill me and my family and my baby." But it's what happened to kylr's other ex-girlfriend almost 10 years ago that's most alarming. Kara was 17 when she went missing. Kara loved her friends, loved being around people, she always had a -- she had a smile -- Reporter: Her parents noticed a personality change after she started dating kylr. His idea was to separate her from us. So he could have the control. The manipulation over her. Reporter: Later, her family says they started noticing bruises and then she told them stories indicating physical and emotional abuse. She said, he grabbed me by the throat, slammed me up into the corner of the door, and said, what are you going to do now ? And she said, dad, I thought he was going to kill me. Reporter: Kara filed an order of protection citing he had a knife and said, I'm going to slit your throat. He has never been charged with any crime related to her disappearance. I have every expectation that had there been enough evidence against kylr to have charged him in that young woman's disappearance, that they most certainly would have. And they haven't. And it's been ten years. Reporter: Yet ten years later he is still a person of interest in that case. I think kylr will be a person of interest forever based on the fact that public opinion has made up its mind. Reporter: For the grieving families, still a long way away from resolution. Just can't imagine it. Until you've experienced it -- had to deal with it, it's really hard to explain. The waiting is the hardest part. I was happy for Jamie when she got the confirmation that it was Jessica. To hear that awful word that it might be a year? I mean, that was just -- that was hard to take. Reporter: Two mothers not leaving each other's side, vowing to fight until justice is served. We're going to make sure that their voice is heard loud and clear. And we're here to get justice for them. Our thoughts are with both families tonight. And of course we'll continue to follow developments in the story.
This transcript has been automatically generated and may not be 100% accurate.