TIBURON, Calif. (WABC) --Robin Williams committed suicide by hanging himself with a belt at his San Francisco Bay Area home, sheriff's officials said Tuesday.
Marin County Sheriff's Lt. Keith Boyd said Williams was found in a bedroom by his personal assistant on Monday at his Tiburon home.
Boyd said toxicology tests will be performed and the investigation is ongoing. The actor also had superficial cuts on his wrist, and a pocketknife was found nearby.
A preliminary investigation had determined the cause of death was suicide due to asphyxia. Williams was 63 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 p.m. Sunday by his wife. She left the home the next morning thinking he was still asleep. His personal assistant later came to the home and became concerned when he knocked on the door and got no response.
His wife, Susan Schneider, released a statement saying, "This morning, I lost my husband and my best friend, while the world lost one of its most beloved artists and beautiful human beings. I am utterly heartbroken. On behalf of Robin's family, we are asking for privacy during our time of profound grief. As he is remembered, it is our hope the focus will not be on Robin's death, but on the countless moments of joy and laughter he gave to millions."
A statement from Williams' representative said "This is a tragic and sudden loss. The family respectfully asks for their privacy as they grieve during this very difficult time."
The White House has released a statement on Williams' passing from President Barack Obama.
"Robin Williams was an airman, a doctor, a genie, a nanny, a president, a professor, a bangarang Peter Pan, and everything in between. But he was one of a kind. He arrived in our lives as an alien -- but he ended up touching every element of the human spirit. He made us laugh. He made us cry. He gave his immeasurable talent freely and generously to those who needed it most -- from our troops stationed abroad to the marginalized on our own streets. The Obama family offers our condolences to Robin's family, his friends, and everyone who found their voice and their verse thanks to Robin Williams."
Williams first moved to the Bay Area when he was a teen and attended Redwood High School in Larkspur and later the College of Marin for theater. He also owned a home in San Francisco's Sea Cliff neighborhood.
From his breakthrough in the late 1970s as the alien in the hit TV show "Mork and Mindy," through his standup act and such films as "Good Morning, Vietnam," the short, barrel-chested Williams ranted and shouted as if just sprung from solitary confinement. Loud, fast, manic, he parodied everyone from John Wayne to Keith Richards, impersonating a Russian immigrant as easily as a pack of Nazi attack dogs.
He was a riot in drag in "Mrs. Doubtfire," or as a cartoon genie in "Aladdin." He won his Academy Award in a rare, but equally intense dramatic role, as a teacher in the 1997 film "Good Will Hunting."
He had a long career as a stand-up comedian and appeared in numerous film and television roles including the 1970s sitcom "Mork and Mindy," his Academy Award-winning performance in "Good Will Hunting" and nominations for "Good Morning, Vietnam," "Dead Poets Society" and "The Fisher King."
His costar from "Mork and Mindy," Pam Dawber, said of Williams' death: "I am completely and totally devastated. What more can be said?!"
Williams also won three Golden Globes, for "Good Morning, Vietnam," "Mrs. Doubtfire" and "The Fisher King."
Like so many funnymen, he had serious ambitions, and played for tears in "Awakenings," "Dead Poets Society" and "What Dreams May Come," something that led New York Times critic Stephen Holden to once say he dreaded seeing the actor's "Humpty Dumpty grin and crinkly moist eyes."
His other film credits included Robert Altman's "Popeye" (a box office bomb), Paul Mazursky's "Moscow on the Hudson," Steven Spielberg's "Hook" and Woody Allen's "Deconstructing Harry." On stage, Williams joined fellow comedian Steve Martin in a 1988 Broadway revival of "Waiting for Godot."
"I dread the word 'art,'" Williams told the AP in 1989. "That's what we used to do every night before we'd go on with 'Waiting for Godot.' We'd go, 'No art. Art dies tonight.' We'd try to give it a life, instead of making "Godot" so serious. It's cosmic vaudeville staged by the Marquis de Sade."
His personal life was often short on laughter. He had acknowledged drug and alcohol problems in the 1970s and '80s and was among the last to see John Belushi before the "Saturday Night Live" star died of a drug overdose in 1982.
Williams announced in recent years that he was again drinking but rebounded well enough to joke about it during his recent tour. "I went to rehab in wine country," he said, "to keep my options open."
More recently, he appeared in the "Night at the Museum" movies, playing President Theodore Roosevelt in the comedies in which Ben Stiller's security guard has to contend with wax figures that come alive and wreak havoc after a museum closes. The third film in the series is in post-production, according to the Internet Movie Database.
In April, Fox 2000 said it was developing a sequel to "Mrs. Doubtfire" and Williams was in talks to join the production.
Williams also made a short-lived return to TV last fall in CBS' "The Crazy Ones," a sitcom about a father-daughter ad agency team that co-starred Sarah Michelle Gellar. It was canceled after one season.
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(Some information for this story is from the Associated Press.)