The ex-husband of first lady Jill Biden has been approached by New York state investigators regarding the 1982 disappearance of Robert Durst’s first wife, according to a report, as a Westchester County grand jury on the millionaire real estate scion-turned-convicted killer is set to convene next week. 

Bill Stevenson, a businessman from Delaware who was previously married to President Biden’s wife, has been approached by state investigators seeking more information about his alleged extramarital affair with Kathie Durst, News 12 Westchester first reported Wednesday, citing several anonymous sources. 

The outlet first sat down with Stevenson for a two-hour interview earlier this year to detail how his lifelong friendship with Kathie Durst took an intimate turn in 1982, days before she went missing. 

He claimed Robert Durst barged in on them and directed violent threats at her. 

REAL ESTATE HEIR ROBERT DURST FOUND GUILTY BY L.A. COUNTY JURY OF KILLING BEST FRIEND 

"The next thing I realize, we hear pounding on the door. It’s like 7:20 in the morning. She runs out of the bedroom and runs back in and says, ‘It’s Bob.’ I jumped up. I ran out," Stevenson previously said in the on-camera interview months ago. "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. It was so crazy, and he started yelling, ‘Kathleen, this isn’t going to happen.’ People have to understand that this guy is a monster." 

News 12 also reported that a Westchester grand jury will convene no later than Monday to look into Durst's connection to Kathie’s disappearance. 

Also citing an anonymous source, The Associated Press previously reported that Westchester District Attorney Mimi Rocah had decided to take the case to a grand jury – but there hadn't been a specific timing for that. This development comes to light a day before 78-year-old Robert Durst, who remains behind bars and battling cancer in California, is expected to be sentenced Thursday for the 2000 killing of his best friend, Susan Berman. 

Prosecutors say Berman was his confidante and helped him cover up Kathie Durst’s killing. 

Durst, the eccentric heir to a family of New York City developers, sat throughout the trial in a wheelchair, spoke slowly in a strained, raspy voice when he testified in his own defense and read his lawyer’s questions from a tablet giving live transcriptions because he struggles with hearing. Los Angeles prosecutors say Durst shot Berman at her Los Angeles home in December 2000 as she was preparing to tell police about her involvement in Kathie Durst’s death. She had told friends she provided a phony alibi for him after his wife vanished, prosecutors said.

"He’s a narcissistic psychopath. He killed his wife and then he had to keep killing to cover it up," Deputy District Attorney John Lewin said after Durst’s conviction in the Los Angeles case.

Kathie Durst was 29 and in her final months of medical school when she vanished on Jan. 31, 1982. She and Robert Durst, who was 38 at the time, had been married nearly nine years and were living in South Salem, near the Connecticut border. Her body was never found. At the request of her family, she was declared legally dead in 2017.

Robert Durst claimed to police that on the night of her disappearance, he’d put her on a train to New York City, had a drink with a neighbor and then spoke with Kathie Durst by telephone while she stayed at their Manhattan apartment. They’d been fighting earlier in the evening, he said. A few weeks before that, Kathie Durst went to the hospital with facial injuries she said were caused by Robert Durst.

In the 2015 HBO documentary "The Jinx: The Life and Deaths of Robert Durst," he admitted he made up the details about seeing his neighbor and talking to Kathie Durst by phone, saying he did so because he was "hoping that would just make everything go away."

In the same documentary, after filmmakers confronted Durst with evidence linking him to Berman’s killing, he stepped off camera and muttered to himself on a live microphone in the bathroom: "Killed them all, of course."

Robert Durst, who divorced Kathie Durst in 1990 citing abandonment, was never charged in her disappearance despite several efforts over the years to close the case. Authorities reopened the case in 1999, searching a lake and the couple’s home.

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While all that was happening, Durst fled to Galveston, Texas, where he was accused of killing a neighbor, Morris Black. Durst then chopped up Black’s body and tossed it out to sea. Durst claimed self-defense — that he and Black were struggling for control of a gun — and was acquitted. He was convicted of destroying evidence for discarding the body parts.

Durst, testifying in the Los Angeles trial, denied killing Kathie Durst. After her medical school called to report that she hadn’t been going to class, he said he figured she was "out someplace having fun" and suggested that perhaps drug use was to blame.

"It hadn’t occurred to me that anything had happened to her," Durst testified in August. "It was more like: What had Kathie done to Kathie?"

The Associated Press contributed to this report.