The former husband of First Lady Jill Biden gave a bombshell interview about his relationship with Robert Durst’s wife Kathie Durst, claiming he had an affair with her just before she disappeared, and that he told police Robert Durst was likely responsible.

Robert Durst is currently on trial for the murder of his good friend Susan Berman, who prosecutors allege he fatally shot in 2000 because she had damning information about Kathie Durst’s disappearance in 1982. Durst has been indicted for murder before, but was acquitted for the death and dismemberment of his roommate who he killed in 2001, arguing self defense.

In an interview with the News 12 show “Turn to Tara,” Bill Stevenson told journalist Tara Rosenblum that he had known Kathie Durst for most of her life, dating back to the time their families would spend vacationing in the Poconos. The two stayed in touch as adults, and Stevenson and his then-wife Jill reportedly hosted Kathie and Robert Durst at their Delaware home in 1974. While Jill and Kathie hit it off, Stevenson said, he didn’t connect with Robert Durst, and recalled seeing Durst talking to himself in his garage.

A few years later, Stevenson said, Kathie Durst called him, frantic, saying she was having “a real problem with Robert” and that he was being violent with her.

Stevenson said he wasn’t exactly sure why Kathie reached out to him.

“I think at that point she really couldn’t trust anybody around her who knew Robert, I guess. I don’t know why she picked me, but I’m glad she did,” he said, immediately adding, “But I do feel like I let her down. I look back at that last two months and go ‘What could I have done differently?”‘

For months after that call, Stevenson, by then divorced, traveled to New York to help his friend make a plan to safely separate from Robert Durst. During one visit, when he and another friend were staying at Kathie’s New York City apartment, he said the night turned romantic – and then took a frightening turn.

“We closed the door and life changed for both of us. Totally unexpected. Beautiful night and no regrets,” Stevenson said about their romantic encounter in her bedroom.

But hours later they were startled awake.

“The next thing I realize there is pounding at the door at 7:30 a.m. She runs out of the bedroom, and then runs back in and says, ‘It’s Bob.’ I jump up. I ran out. And then all of a sudden, he screams something. He had a wad of cash rolled up and hit her right in the face with it, and it was so crazy, and he started yelling, ‘Kathleen, this isn’t going to happen,'” Stevenson said.

“And she started yelling, ‘I’m moving to Delaware. I’m moving to Delaware. I’m done.’ and I’m like, sitting there. I’m in shock. People have to understand that this guy is a monster – I saw it in his eyes.”

Only 10 days later, Kathie Durst disappeared. And while it took decades for Stevenson to speak publicly, he said in the interview that he went to police right away with his concerns.

“I got in my car and went to the 19th Precinct, literally within 24 hours. And I said, ‘He killed her,'” Stevenson said. “[The officer] wrote a couple of things down. He goes, ‘We’ll get back to you.’ I never heard another word from them.”

Members of Kathie Durst’s family reportedly confirmed to News 12 that Kathie had mentioned her time with Stevenson, who described himself a “the missing link” in the investigation. He also said he believes the affair may have driven Robert Durst to violence, but that he doesn’t regret the encounter.

“Absolutely, I think it would have driven him crazy. And I don’t feel guilty about that. He was abusing her and she wanted out. I do not regret that. The minute I saw her standing there and she grabbed my hand, it was all I could think about. I’ve got to be honest, and if it led to him going off the deep end I think, and at that point, I don’t regret it. Not a second,” says Stevenson.

“I feel if something was wonderful at the end of her life, I hope this was it. I just hope she had the same thoughts at the end there.”

Kathie Durst is presumed dead but her body has never been found.

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