Although an official cause of death has not yet been released, the Marin County Coroner's office confirmed there is suspicion Williams died of "suicide due to asphyxia."
He was discovered at his home in Tiburon around 11:55 a.m. PST and pronounced dead at the scene.
Williams' publicist issued the following statement on Monday:
"Robin Williams passed away this morning. He has been battling severe depression of late. This is a tragic and sudden loss. The family respectfully asks for their privacy as they grieve during this very difficult time."
Williams' last Twitter and Instagram posts were dated July 31, wishing daughter Zelda Rae a happy 25th birthday: "Quarter of a century old today but always my baby girl. Happy Birthday Zelda Williams. Love you!"
Williams won an Academy Award in 1997 for his film with Matt Damon, Good Will Hunting and that same year was declared by Entertainment Weekly "the funniest man alive." Williams was also the winner of two Emmy Award, four Golden Globes, two Screen Actors Guild Awards and five Grammy Awards. He received three additional Oscar nominations for his roles in The Fisher King (1991), Dead Poets Society (1989) and Good Morning, Vietnam (1987).
The third installment of Night at the Museum, in which Williams plays President Theodore Roosevelt, is scheduled to be released in December.
Williams is survived by his third wife Susan Schneider and three children: Zachary Pym (31) from his first marriage to Valerie Velardi, and Zelda Rae (25) and Cody Alan (22) from his second marriage to Marsha Garces.