The damning evidence HBO uncovered about a real-estate heir accused of murder

HBO producers may have helped solve a 15-year-old murder by uncovering an incriminating letter written by Robert Durst, a wealthy real-estate heir who was arrested on Sunday for allegedly killing his friend.

Durst was the subject of a new HBO documentary series called "The Jinx," about the cloud of suspicion hanging over him after the unsolved 2000 murder of the journalist Susan Berman.

That documentary unearthed a "startling piece of evidence" - a letter that Durst had written to Berman, as the Guardian reported this weekend.

Durst - whose wife disappeared mysteriously in 1982 - was a close friend of Berman's and was considered a suspect in her murder. A year after she was shot execution-style, Durst killed his neighbor but was acquitted when a jury found he'd acted in self-defense, according to The New York Times.

The damning letter Durst wrote Berman contained block letters and a misspelling of "Beverly Hills" that resembled a note sent to police after Berman's death that alerted them to a "cadaver" at her residence.

After Durst was asked about that letter, he went into the bathroom by himself. "There it is. You're caught," he muttered to himself, apparently not realizing a microphone was picking up his words. "What the hell did I do? Killed them all of course."

Susan Berman, magazine journalist and daughter of Las Vegas mobster Davie Berman, was shot in the back of the head on Dec. 23, 2000 in her Hollywood Hills home. With no signs of a break-in, police concluded that Berman's murderer must have been someone she knew.

In 2000, Durst was named the prime suspect in a reopened investigation into his wife Kathy's 1982 disappearance from their Westchester County home. Upon learning this, Durst disguised himself as a mute woman and fled from New York to Galveston, Texas.

Durst claimed in "The Jinx" that his last correspondence with Berman was in early 2000, when she called to tell him that the LAPD had contacted her about Kathy's disappearance.

He then wired her $50,000 after she told him she needed financial help. Berman was found murdered a few months later, and investigators have speculated over whether or not this $50,000 was a bribe to keep her from talking to the police.

The following year, Durst killed his 71-year-old neighbor Morris Black, dismembered him, and dumped his body parts in the Galveston Bay. Durst successfully argued that he had killed Black in self-defense and was eventually acquitted of murder.