Williams, who was 63 years old, was found unresponsive in his home in Tiburon, 17 miles (27 km) north of San Francisco.
According to the coroner's division of the Marin Sheriff's Office, a 9-1-1 operator received a call at approximately 11:55 a.m. regarding Williams, who was unconscious and not breathing in his home, which he shares with his wife. It is unclear who made the call.
Within minutes, Marin County sheriff's deputies, as well as Tiburon and Marin fire authorities, arrived at Williams' home.
"At this time, the Sheriff's Office coroner's division suspects the death to be a suicide due to asphyxia, but a comprehensive investigation must be completed before a final determination is made," the coroner's office said in a statement.
"A forensic examination is currently scheduled for August 12, 2014 with subsequent toxicology testing to be conducted," the statement added.
Williams rose to fame as the alien Mork in the ABC television sitcom
"Mork and Mindy" (1978-82) after paying his dues on the standup comedy circuit. He went on to star in many feature films, both comedies and dramas, including
Good Morning, Vietnam (1987),
Dead Poets Society (1989),
Awakenings (1990),
The Fisher King (1991),
Alladin (1992),
Mrs. Doubtfire (1993),
Jumanji (1995),
The Birdcage (1996),
Good Will Hunting (1997),
Night at the Museum (2006) and
Happy Feet (2006).
He won the Academy Award for Best Supporting Actor for his role in
Goodwill Hunting. Williams also received two Emmy Awards, four Golden Globes, two Screen Actors Guild Awards and five Grammy Awards.
Williams fought a longtime battle against depression, drug and alcohol addition.
According to his publicist, Williams had been suffering severe depression and had
spent time in rehab as recently as last month.
Susan Schneider, Williams' wife, released the following statement:
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. 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 that the focus will not be on Robin's death but on the countless moments of joy and laughter he gave to millions.