Preliminary findings suggest that Williams' death was caused by suicide due to asphyxia, said Boyd. The actor also had superficial cuts on his wrist and a pocketknife was found nearby.
Williams was last seen at his home at 10 p.m. on Sunday. His wife went to sleep at 10:30 p.m. that night. It's not known what time Williams turned in, but Boyd said Williams retreated to a different room than his wife. His wife left the home in the morning believing Williams was still asleep and returned there after receiving a call about his death.
The comedian's personal assistant became worried on Monday after Williams didn't respond to knocks on the door at around 11:45 a.m. The assistant found Williams in the room, where he was "slightly suspended in a seated position."
Williams was pronounced dead at age 63 at 12:02 p.m.
Boyd didn't confirm whether Williams left a note.
Authorities will continue to investigate his death and said that toxicology test results won't be completed for 2-6 weeks. Once those are in, another press conference will be held.
Earlier this summer, Williams entered a rehab facility to help him maintain long-term sobriety. Williams battled drug and alcohol addiction in the '70s and early '80s before going sober for some 20 years. He slipped back into using again, entering a substance abuse rehab center to tackle alcoholism in 2006.
The Oscar winner recently sought treatment for depression.
He had been busy in Hollywood as of late, recently starring in the short-lived CBS series "The Crazy Ones," alongside Sarah Michelle Gellar. He had several movies coming up, including "Boulevard" with Bob Odenkirk, a new "Night at the Museum" installment and a "Mrs. Doubtfire" sequel.
Tributes have been pouring in for Williams, the star of such classics as "Mrs. Doubtfire," "Dead Poets Society" and "Good Will Hunting."
Various pop-up memorials have been set up, too, including at the bench from "Good Will Hunting."
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