In court Monday, Los Angeles prosecutor John Lewin played audio recordings from two jailhouse calls made by Robert Durst, the Manhattan real estate heir standing trial for murder, in which he appears to plot to kill his brother, Douglas Durst, CEO of the Durst Organization, one of the largest residential real estate firms in New York City.

In a Dec. 21, 2001, call to his wife Debrah Charatan, Robert Durst talked about “Igoring” a person he called “BM,” whom the prosecution believes to be Douglas—a reference to the CEO’s dogs, all named “Igor,” which Robert Durst has been accused of killing. In an interview from 2012, with Andrew Jarecki, director of HBO’s 2015 docuseries about Durst, The Jinx, the heir had denied saying he had planned to “Igor” his brother.

Lewin also presented a series of statements from witnesses who said they saw Durst approach Douglas’ homes and workplace. In May 2008, a security guard said he witnessed Durst come up to the driveway of Douglas’ residence in Katonah, New York, wearing a blue ski mask with eye openings pulled back on his forehead. When the guard pulled his firearm on Durst, the heir reportedly accelerated in reverse and sped away from the house.

Later, in April 2012, two security professionals cited seeing Durst approach the West 43rd Street building where Douglas’ son, Alexander, lives. Durst declined to explain his presence, and the guards called the police, who filed a report. The following year, on June 2, 2013, a Durst Organization employee spotted the heir scoping out the residences of Douglas and his daughter Helena Durst. The reports were later corroborated by surveillance footage.

The two brothers have had a fraught relationship since the early 1990s, when Robert Durst, the eldest brother, was passed over as successor to his father’s company in favor of Douglas. In a 2015 interview with prosecutor John Lewin, Durst admitted: “Douglas wanted to take my birthright. He wanted to run the company. He wanted to take my money. And he did those things.”

In 2001, after Durst jumped bail for separate charges, he was arrested for shoplifting at a Pennsylvania market. Authorities found in his possession a note that stated: “What DD is doing to me, puts me in the same place, as what Kathy did to me.” Prosecutors argue the note explicitly links his mental state on Douglas to the way he was feeling about his long missing wife Kathleen Durst around the time she disappeared in 1982.

Durst has been implicated in the disappearances of three people: Kathleen Durst; his best friend Susan Berman, who was shot in her home in 2000; and Morris Black, a 71-year-old resident of Galveston, Texas, and Durst’s former neighbor, who was shot and dismembered in 2001. Durst has denied involvement in his wife’s disappearance and was acquitted of Black’s murder, though he admitted to dismembering the man’s body.

He is currently on trial for Berman’s murder. He has pleaded not guilty. The case is expected to last five months.