A preliminary investigation has determined the cause of death of actor-comedian Robin Williams was suicide due to asphyxia, according to the sheriff's office in Marin County, California.

Williams, the Academy Award winner and comic supernova whose explosions of pop culture riffs and impressions dazzled audiences for decades and made him a gleamy-eyed laureate for the Information Age, died today at the age of 63.

He was pronounced dead at his home in California, according to the sheriff's office in Marin County, north of San Francisco.

"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," said Williams' wife, Susan Schneider. "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,"

Williams had been battling severe depression recently, said Mara Buxbaum, his press representative. Williams, who struggled with drug and alcohol abuse earlier in this career, also spent time at Minnesota's Hazelden Addiction Treatment Center in recent months, with Buxbaum issuing a statement in July saying that Williams was "simply taking the opportunity to fine-tune and focus on his continued commitment, of which he remains extremely proud."

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 was no less on fire in interviews. During a 1989 chat with The Associated Press, he could barely stay seated in his hotel room, or even mention the film he was supposed to promote, as he free-associated about comedy and the cosmos.

"There's an Ice Age coming," he said. "But the good news is there'll be daiquiris for everyone and the Ice Capades will be everywhere. The lobster will keep for at least 100 years, that's the good news. The Swanson dinners will last a whole millennium. The bad news is the house will basically be in Arkansas."

Following Williams on stage, Billy Crystal once observed, was like trying to top the Civil War. In a 1993 interview with the AP, Williams recalled an appearance early in his career on "The Tonight Show Starring Johnny Carson." Bob Hope was also there.

"It was interesting," Williams said. "He was supposed to go on before me and I was supposed to follow him, and I had to go on before him because he was late. I don't think that made him happy. I don't think he was angry, but I don't think he was pleased.

"I had been on the road and I came out, you know, gassed, and I killed and had a great time. Hope comes out and Johnny leans over and says, 'Robin Williams, isn't he funny?' Hope says, 'Yeah, he's wild. But you know, Johnny, it's great to be back here with you."'

In 1992, Carson chose Williams and Bette Midler as his final guests.

Like so many funnymen, he had serious ambitions, winning his Oscar for his portrayal of an empathetic therapist in "Good Will Hunting." He also 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."

Williams also won three Golden Globes, for "Good Morning, Vietnam," "Mrs. Doubtfire" and "The Fisher King."

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."

Born in Chicago in 1951, Williams would remember himself as a shy kid who got some early laughs from his mother -- by mimicking his grandmother. He opened up more in high school when he joined the drama club and he was accepted into the Juilliard Academy, where he had several classes in which he and Christopher Reeve were the only students and John Houseman was the teacher.

Encouraged by Houseman to pursue comedy, Williams identified with the wildest and angriest of performers: Jonathan Winters, Lenny Bruce, Richard Pryor, George Carlin. Their acts were not warm and lovable. They were just being themselves.

"You look at the world and see how scary it can be sometimes and still try to deal with the fear," he told the AP in 1989. "Comedy can deal with the fear and still not paralyze you or tell you that it's going away. You say, OK, you got certain choices here, you can laugh at them and then once you've laughed at them and you have expunged the demon, now you can deal with them. That's what I do when I do my act."

He unveiled Mork, the alien from the planet Ork, in an appearance on "Happy Days," and was granted his own series, which ran from 1978-82.

In subsequent years, Williams often returned to television -- for appearances on "Saturday Night Live," for "Friends," for comedy specials, for "American Idol," where in 2008 he pretended to be a "Russian idol" who belts out a tuneless, indecipherable "My Way."

Williams also could handle a script, when he felt like it, and also think on his feet. He ad-libbed in many of his films and was just as quick in person. During a media tour for "Awakenings," when director Penny Marshall mistakenly described the film as being set in a "menstrual hospital," instead of "mental hospital," Williams quickly stepped in and joked, "It's a period piece."

Winner of a Grammy in 2003 for best spoken comedy album, "Robin Williams -- Live 2002," he once likened his act to the daily jogs he took across the Golden Gate Bridge. There were times he would look over the edge, one side of him pulling back in fear, the other insisting he could fly.

"You have an internal critic, an internal drive that says, 'OK, you can do more.' Maybe that's what keeps you going," Williams said. "Maybe that's a demon. ... Some people say, 'It's a muse.' No, it's not a muse! It's a demon! DO IT YOU BASTARD!! HAHAHAHAHAHAHA!!! THE LITTLE DEMON!!"