Robin Williams committed suicide by hanging himself with a belt at his California home, Lt. Keith Boyd of the Marin County Sheriff's Office said Tuesday during a press conference revealing preliminary findings surrounding the actor's death.
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 and returned there after receiving a call about his death.
Williams' personal assistant became worried on Monday when he knocked on the door and didn't get a response. The assistant found Williams on in the room, where he was "slightly superseded in a seated position."
On Monday morning just before 11:55 a.m., an emergency call was made from a "distraught" caller who said Williams had been unconscious and not breathing.
Williams was pronounced dead at age 63.
Boyd didn't confirm whether Williams left a note.
Authorities will continue to investigate his death and that toxicology test results won't be completed for weeks.
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.
Williams recently starred 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.