SAN FRANCISCO: President Barack Obama has led tributes to US actor and comedian Robin Williams, who was found dead in an apparent suicide in San Francisco Bay Area, California.

Marin County Police in California said Williams was pronounced dead at his home after officials responded to an emergency call around noon local time on Monday.

Williams, 63, was the funniest guy in the room, something that made it all the harder for friends and fans to accept that beneath that reservoir of frenetic energy and seemingly endless good humor resided demons so dark they could push him to suicide.

It was no secret that the Oscar-winning actor had suffered for years from periodic bouts of substance abuse and depression — he made reference to it himself in his comedy routines. But word that he had killed himself at his home left both friends in the Hollywood community and neighbors in the quiet neighborhood of Tiburon that he called home equally stunned and grief-stricken.

He was last seen alive at home Sunday, according to the Marin County coroner’s office. Shortly before noon, the Sheriff’s Department received an emergency call from the home, where the star of “Good Will Hunting,” “Mrs. Doubtfire,” “Good Morning, Vietnam” and dozens of other films was pronounced dead.

Sheriff’s officials said a preliminary investigation determined the cause of death was suicide due to asphyxia.

“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. Just last month, he announced he was returning to a 12-step treatment program he said he needed after 18 months of nonstop work. He had sought treatment in 2006 after a relapse following 20 years of sobriety.

Williams joked about that during a comedy tour, saying, “I went to rehab in wine country to keep my options open.”

Likewise, when word spread about his struggles with drugs in the early 1980s, Williams responded with a joke that for a time became a catchphrase for his generation’s recreational drug use.

His struggles never seemed to affect his talent.

“You look at the world and see how scary it can be sometimes and still try to deal with the fear,” he said 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.”

From his breakthrough in the late 1970s as the alien in the hit TV show “Mork & Mindy,” through his standup act and numerous hit films, the short, barrel-chested Williams ranted and shouted as if just sprung from solitary confinement. Loud, fast and manic, he parodied everyone from actor John Wayne to Keith Richards, impersonating a Russian immigrant as easily as a pack of Nazi attack dogs.