Robert Durst, the real estate heir who was sentenced to life in prison for murder on Thursday, is very sick with COVID-19 and has been placed on a ventilator, his lawyer told HuffPost on Saturday.

“I was very concerned about his condition Thursday in court. He was having difficulty breathing and speaking and was very weak,” attorney Dick DeGuerin wrote in an email, noting that he was getting tested for the disease as a precaution.

Durst, 78, slumped down in his wheelchair and appeared to have difficulty communicating in the courtroom, speaking in a hoarse voice. He had been convicted in September for the execution-style killing of his friend Susan Berman in 2000.

Prosecutors allege that Durst feared Berman would give up information about the mysterious 1982 disappearance of his first wife, Kathleen McCormack, who is presumed dead.

While he was once the heir apparent to the Durst family’s New York real estate business ― the family owns some of Manhattan’s most prestigious property ― Durst’s volatile personality proved unsuitable. His younger brother, Douglas Durst, took over the business instead.

A 2015 HBO documentary about Durst, “The Jinx,” helped bring attention to the bizarre circumstances of his life and family history.

Durst went to trial for murder in 2003 in a separate killing, after he moved to Texas and began living in disguise. Durst eventually admitted to dismembering his neighbor, Morris Black, and dumping the parts of his body in a waterway. In Durst’s telling, he was trying to defend himself when Black’s gun went off and killed him.

He was acquitted of the killing, serving only around one year in jail for skipping out on his bail.

Durst is currently facing renewed scrutiny over his suspected role in the death of McCormack; a New York prosecutor is reportedly seeking to indict him.

This week, family members of Berman’s implored Durst to reveal whatever he knows about the location of McCormack’s body shortly before a Los Angeles judge handed down his sentence.