During a news conference on Tuesday, sheriff's officials said Robin Williams committed suicide by hanging himself at his San Francisco Bay Area home.
The official cause of death in the preliminary report is asphyxia due to hanging.
The actor was found in a seated position, slightly off the ground, with a belt around his neck.
Marin County Sheriff's Lt. Keith Boyd also said Tuesday that superficial cuts were found on Williams' wrist and a pocket knife was found nearby.
Toxicology results on whether Williams had any drugs or alcohol in his system are several weeks away.
Williams was 63-years-old and had suffered for years from periodic bouts of substance abuse and depression.
Williams' press representative Mara Buxbaum said the actor had been battling severe depression recently. Just last month, Williams announced he was returning to a 12-step treatment program.
Coroner's officials say he was last seen alive at home around 10:30 p.m. Sunday. His wife went to bed at that time. It was not known when Williams retired to another room in the home.
SLIDESHOW: The life of Robin Williams
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