SAN RAFAEL, CALIF. (AP) - Oscar-winner Robin Williams, whose free-form comedy and adept impressions dazzled audiences for decades, has died in an apparent suicide. He was 63. 

The Marin County Sheriff's Office says Williams was pronounced dead at his home in California on Monday. The sheriff's office says a preliminary investigation shows the cause of death to be a suicide due to asphyxia.

Williams shot to fame in the late `70s as the alien in TV's “Mork and Mindy.'' He conquered the big screen in comic films such as “Good Morning, Vietnam'' and “Mrs. Doubtfire.'' But he won his academy award in a serious role - as the therapist in “Good Will Hunting.''

His performing style was at its purest in his standup act, as he impersonated a Russian immigrant or parodied anyone from John Wayne to Keith Richards.

Williams' wife Susan Schneider released a statement Monday, 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." She added, "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."

His press representative, Mara Buxbaum, said Williams had recently been battling severe depression.

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Celebrity colleagues and admirers of Robin Williams shared their reactions Monday to his death at age 63 in an apparent suicide:

- “I am completely and totally devastated. What more can be said?'' - Pam Dawber, in a statement.

- “Robin was a lightning storm of comic genius and our laughter was the thunder that sustained him.  He was a pal and I can't believe he's gone.'' - Steven Spielberg, in a statement.

-"I could not be more stunned by the loss of Robin Williams, Mensch, great talent, acting partner, genuine soul.'' - Steve Martin, on twitter.

- “I saw him on stage the very first time he auditioned at the Improv and we have been friends ever since. It's a very sad day.'' - Jay Leno, in a statement.

- “We have lost one of our most inspired and gifted comic minds, as well as one of this generation's greatest actors. To watch robin work, was a magical and special privilege. His performances were unlike anything any of us had ever seen, they came from some spiritual and otherworldly place. He truly was one of the few people who deserved the title of `genius.''' - Chris Columbus, in a statement. 

- “Robin was as sweet a man as he was funny. If you're sad, please tell someone.'' - Jimmy Kimmel, on twitter.

- "Robin was friend, boss, brother, inspiration. His generosity and intelligence knew no limits.'' - Harvey Fierstein, on twitter.

- “I've never known a sweeter, brighter, more considerate person than robin. Robin's commitment as an artist to lifting our mood and making us happy is compared to none. He loved us all and we loved him back.'' - John Travolta, in a statement.

- ``a big tenacious overflowing hyperkinetic eruption of compassion would be (the) best tribute to williams.'' - John Cusack on twitter.

- “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.'' - President Barack Obama, in a statement.