UPDATED March 15, 2015, 11:23 p.m. ET

The case of Robert Durst, the estranged heir to a New York real estate fortune, took another bizarre turn Sunday night when HBO's The Jinx broadcast a recording in which Durst appears to admit to murdering his friend and possibly his wife. In the clip, Durst was apparently unaware that he was being taped as he spoke to himself in a bathroom, mumbling that he had "killed them all."

The final episode of the documentary series, which concluded with the previously unseen clip, came just a day after Durst was arrested in New Orleans.

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Just before the bathroom recording, Durst had been confronted in an interview with new evidence that may show that he wrote a letter to the police notifying them of the 2000 murder of his friend, Susan Berman. Durst denied that he had written the letter.

After the interview, Durst asked to use the bathroom, but still had a microphone attached to his clothing. He is then heard saying what sounds like, "There it is. You're caught," and "What the hell did I do? Killed them all, of course."

That audio was not discovered for more than two years after the filming of the interview, according to The New York Times, which also said there is some doubt as to whether it will be admissible in court.

The show did not provide further information about what Durst might have been referring to in his bathroom soliloquy.

Durst was arrested by FBI agents Saturday at a J.W. Marriott hotel in New Orleans, according to multiple reports.

Durst had made headlines for his suspected involvement in three deaths: Berman's in 2000, the 1982 disappearance of his first wife, Kathleen Durst, for which he was never charged, and the 2001 death of a neighbor in which Durst was found not guilty after pleading self defense. Durst became even more well-known in February after HBO began airing The Jinx: The Life and Deaths of Robert Durst.

The 71-year-old was arrested on an extradition warrant from Los Angeles, according to ABC's Houston affiliate. Durst's lawyer reportedly confirmed that he will face murder charges, but will not fight extradition back to L.A.

It was not not clear if the hot mic incident from the Jinx finale is the reason why he was arrested, or if there is other evidence authorities are acting on.

Durst was previously a person of interest, but was never charged in the shooting death of Berman, his longtime friend who had moved to Los Angeles. In The Jinx's most recent episode, one of the show's producers comments that a 1999 letter written from Durst to Berman strongly resembles the anonymous letter sent to police in 2000, notifying them of a "cadaver" at Berman's home. The handwriting appears similar and Beverly Hills is misspelled as "Beverley" both times.

Recently, the Los Angeles district attorney reopened Berman's case, according to The New York Times.

Meanwhile, the case involving Kathleen Durst, who disappeared in 1982, remains unsolved. But Jeanine Pirro, the Westchester County district attorney, reopened the case in 2000, and has aggressively and publicly pursued Durst as a suspect since then. She has also appeared on The Jinx.

By 2000, Durst moved to Galveston, Texas, a beach community about 60 miles outside Houston, and posed as a mute woman. Durst admitted to killing his neighbor in Galveston, then dumping the remains in Galveston Bay, but was acquitted after his lawyers successfully argued self-defense.

Durst is the eldest son of real estate mogul Seymour Durst, who died in 1995. Joseph Durst, Seymour's father, founded The Durst Organization — one of New York City's most powerful real estate companies — in 1915. Forbes estimated the family's net worth at $4.4 billion in 2014.

Douglas Durst, brother of Robert Durst and current chairman of The Durst Organization, released a statement to CNBC.

"We are relieved and also grateful to everyone who assisted in the arrest of Robert Durst. We hope he will finally be held accountable for all he has done," Douglas Durst said.

UPDATED 9:55 p.m. ET to reflect the accurate quote from Robert Durst in the final episode of "The Jinx" as "What the hell did I do? Killed them all, of course."



