Oscar-winning actor and comedian Robin Williams died from suspected suicide after battling depression, triggering an outpouring of tributes to one of the most beloved entertainers of his generation.
The 63-year-old star of Hollywood hits such as "Good Will Hunting", "Good Morning Vietnam" and "Mrs Doubtfire" was found dead at his home in Tiburon, northern California, shortly before midday, a police statement said.
Williams' only daughter Zelda has posted a heartfelt tribute to her late father, in a loving response to his final Instagram post.
The 25-year-old posted a quote from children's book The Little Prince by Antoine De Saint-Exupery on Twitter.
"You - you alone will have the stars as no one else has them," the quote said.
"In one of them I shall be laughing. And so it will be as if all the starts were laughing, when you look at the sky at night... You - only you - will have stars that can laugh."
It was signed off with the words: "I love you. I miss you. I'll try to keep looking up".
The veteran actor’s publicist said the funnyman had been suffering from depression prior to his death, and Williams had spoken openly in the past about his battles with alcoholism and drug abuse.
Weeks earlier, Williams spent time in the Hazelden Addiction Treatment Center in Minnesota, which helps patients maintain long-term sobriety.
His press representative Mara Muxbaum said: "Robin Williams passed away this morning.
"He had 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."
In a statement, William's wife Susan Schneider said: "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 the focus will not be on Robin's death, but on the countless moments of joy and laughter he gave to millions."
A statement from the Marin Sheriff's office said a 911 emergency call around 11.55am (local time) reported a male had been found unconscious and not breathing inside the home he shared with his wife.
The male subject was pronounced deceased at 12.02pm and was identified as Robin McLaurin Williams.
"At this time, the Sheriff's Office Coroner Division suspects the death to be suicide," the statement said.
An investigation is under way and a forensic examination, including toxicology testing, is scheduled.
News of Williams death quickly supplanted Iraq from the top item on evening news bulletins as the entertainment world reacted with shock.
US President Barack Obama led tributes to an entertainer he described as “one of a kind” while Hollywood titan Steven Spielberg, a close friend, paid tribute to a comic genius.
"Robin was a lightning storm of comic genius and our laughter was the thunder that sustained him," said Spielberg in a statement cited by Variety.
"He was a pal and I can't believe he's gone," added Spielberg, who famously phoned Williams to cheer himself up during filming of his harrowing 1994 Holocaust drama "Schindler's List".
Spielberg's tribute was echoed throughout the entertainment industry.
"I can't believe the news about Robin Williams. He gave so much to so many people. I'm heartbroken," comic and talkshow host Ellen DeGeneres said on Twitter.
Fellow comedian Steve Martin added: "I could not be more stunned by the loss of Robin Williams, mensch, great talent, acting partner, genuine soul."
Oscar-winning actor Jared Leto paid tribute to a "brave, original artist."
"You taught us how to stand on the edge, fearless, + shine," Leto said on Twitter.
Williams is best known for both comedic and dramatic roles in films including Dead Poets Society, Mrs Doubtfire and Good Will Hunting, for which he won an Oscar for Best Supporting Actor in 1997.
He has won a string of Golden Globes and Emmys.
He even managed to cause a political stir in Australia when he angered Kevin Rudd after jokingly referring to Aussies as “English rednecks” on US TV.
He apologised to the then-prime minister, and offered to take him to a strip club the next time he visited the US.
Born in Chicago in 1951, Williams first achieved fame with his break-out role as the alien Mork in the TV series Mork and Mindy.
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.
On screen, his characters were often offbeat and eccentric - from the zany Mork from the planet Ork to the divorced dad who transforms himself into a elderly British nanny in Mrs Doubtfire.
His skill at imitating voices was often showcased - as in his portrayal of the genie in the 1992 Disney adaptation of Aladdin, in which his character runs through a string of celebrity impressions.
He conquered the big screen in comic films such as Good Morning, Vietnam and won his Academy Award in a serious role - as the therapist in Good Will Hunting.
Williams stars in the CBS series The Crazy Ones and the film The Angriest Man in Brooklyn, which was released in May.
He had recently signed a deal to appear in a sequel of Mrs Doubtfire.
He reprised his role in the third instalment of Night at the Museum, due out in December, and was last seen in the movie The Face of Love, opposite Annette Bening.
For all Williams Hollywood success and outsize public persona, the comedian faced private demons, including recurring battles with drugs, alcohol and mental illness.
He quit drinking and cocaine in the early 1980s, when his first son Zak was born in 1983, but after 20 years sober, he started drinking again while filming in Alaska in 2003, he told the Guardian newspaper in 2010.
“It was that thing of working so much, and going ’Fuck, maybe (drinking) will help?’ And it was the worst thing in the world,” he told the newspaper, adding, however, he did not start taking drugs again.
It took him another three years to get back to sobriety, after a family intervention led him to rehab, he said, blaming his drinking for the breakup in 2008 of his 19-year second marriage to Marsha Garces, Zak’s nanny whom he married in 1989, a year after his first marriage ended in divorce. They had two children, Zelda, 25, and Cody, 22.
“You know, I was shameful, and you do stuff that causes disgust, and that’s hard to recover from.”
It was health problems - and open heart surgery - in 2009 that he credits with being the true turning point.
“It breaks through your barrier, you’ve literally cracked the armour. And you’ve got no choice, it literally breaks you open. And you feel really mortal,” he said.
During the three-hour surgery, doctors replaced Williams’ aortic valve, repair his mitral valve, and correct an irregular heart beat.
The actor was also reportedly diagnosed with bipolar disorder and in July 2014, he checked into a Minnesota rehab facility for help maintaining sobriety after a gruelling year-and-a-half of work.
Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.