Oscar-winning actor and comedian Robin Williams was found dead Monday inside his California home after hanging himself with a belt, stunning his devoted fans and fellow actors.

Keith Boyd, the Marin County assistant chief deputy coroner, said Tuesday that the preliminary cause of death appeared to be asphyxia due to hanging. Boyd said emergency personnel responded to a 911 call from Williams' home around noon on Monday, and it appeared rigor mortis had already set in. Williams was pronounced dead shortly afterward.

Williams had been found dead in his bedroom, fully clothed, with a belt around his neck and the other end wedged between a door and the frame.

A knife was also found nearby and there were superficial cuts on his wrists. Boyd did not indicate if there was a suicide note. Toxicology reports will not be available for a few more weeks.

His wife had last seen him at approximately 10:30 p.m. on Sunday, when she had gone to bed and then Williams went to a different room in the home. She left the house around 10:30 a.m. the next day, believing Williams was still sleeping. It's unclear what time Williams' death occurred.

Williams, 63, known for both his comedic genius and dramatic aptitude, had recently been battling depression, said his representative, Mara Buxbaum, in a statement.

For years Williams battled alcohol and drug addiction, most recently checking himself in to a Minnesota facility in July.

A spokesman for Williams said last month he had not relapsed and had been sober for 20 years.

His wife, Susan Schneider, said she plans on remembering Williams by the “countless moments of joy and laughter he gave to millions."

“This morning, I lost my husband and my best friend, while the world lost one of its most beloved artists and beautiful human beings,” Schneider added in a statement. “I am utterly heartbroken.”

His daughter, actress Zelda Williams, on Tuesday tweeted a quote from Antoine De Saint-Exupery and wrote "I love you. I miss you. I'll try to keep looking up. Z."

Three weeks ago, Williams celebrated his birthday by posting a photo of himself with a monkey on Instagram. And on July 31 Williams posted a photo of him and his daughter many several years ago.

“Quarter of a century old today but always my baby girl,” he wrote. “Happy Birthday ... Love you!”

Williams has starred in dozens of films. Some of his most well known roles include the cross-dressing nanny in “Mrs. Doubtfire,” the funny genie whose only wish is for freedom in “Aladdin,” the spirited cabaret owner in “The Birdcage” and the thoughtful therapist and teacher in “Good Will Hunting,” for which he won the academy award for best supporting actor.

Williams received his first Oscar nomimation for his role in “Good Morning, Vietnam.”

Williams was involved in several films not yet released, including “Night at the Museum: Secret of the Tomb,” set to premier in December.

President Barack Obama offered heartfelt condolences to Williams' friends, family and "and everyone who found their voice and their verse thanks to Robin Williams" following news of his death. Williams "gave his immeasurable talent freely and generously," Obama added.

"Robin Williams was an airman, a doctor, a genie, a nanny, a president, a professor, a bangarang Peter Pan, and everything in between," Obama said in a statement. "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."

Celebrities took to Twitter Monday evening to voice their grief over the loss of an icon.

“I could not be more stunned by the loss of Robin Williams,” Steve Martin wrote on Twitter, “mensch, great talent, acting partner, genuine soul.”

Fellow comedian Sarah Silverman called losing Williams “terrible ... By all accounts he was pure love.”

Williams appeared on “Sesame Street” several times throughout the 1990s and 2000s.

“We mourn the loss of our friend Robin Williams,” the kids show wrote with a picture of Williams with the two-headed monster, “who always made us laugh and smile.”

A forensic examination is scheduled for Tuesday, the corner’s division said. Authorities will also perform a toxicology report.

Williams wasn’t the only celebrity to die tragically and too young this year. In February, Philip Seymour Hoffman died inside his West Village apartment of a drug overdose. He was 46.

(With CAROLINE LINTON, DAN RIVOLI and SHEILA ANNE FEENEY)