Comedian Robin Williams died of hanging on Monday morning, said Marin County sheriffs.

Lieutenant Keith Boyd made the announcement at a Tuesday press conference at the Marin County Sheriff’s Office in San Rafael, Calif.

Boyd said that Williams, 63, was suspended with a belt around his neck. He was clothed and rigor mortis had set in. Police said the actor was found by his assistant in a seated position in his home in Tiburon, just north of San Francisco.

There were also superficial wounds found on one of his wrists, said Boyd, indicating that Williams may have tried to slash his wrist before the hanging. A pocket knife was also found nearby the scene.

An investigation is ongoing into his death, which was due to asphyxia. His publicist noted that the actor had been struggling with depression as of late, and recently entered a 12-step rehab for drug abuse.

Williams was last seen alive by his wife on Sunday night.

The investigation is ongoing. A toxicology report will be conducted but will take two to six weeks to be completed.