The 63-year-old actor and comedian's death by suspected suicide shocked the world yesterday, and fans and friends were quick to pay tribute to the award-winning star of more than 100 films and shows.
His body of work spanned television and the big screen, and included films Good Will Hunting, Hook, Mrs Doubtfire and Good Morning, Vietnam.
Robin Williams killed himself at his San Francisco-area home, sheriff's officials said this morning.
Marin County Sheriff's Lt. Keith Boyd said Williams was found in a bedroom by his personal assistant on Monday (Tuesday NZ time).
Sheriff's officials said Williams was 63 and had periodic bouts of substance abuse and depression.
Authorities also confirmed chemical substances were found in his system.
Toxicology results will not be made available for approximately two-six weeks so further tests can be carried out.
Williams' press representative Mara Buxbaum said the actor had been battling severe depression recently. Just last month, Williams announced he was returning to a 12-step treatment programme.
Coroner's officials say he was last seen alive at home around 10pm Sunday.
Shortly before noon on Monday, the Sheriff's Department received an emergency call from the home, where the star was pronounced dead.
Described as a genius, the celebrated actor and comedian, who had battled alcohol and drug addition, once said: "In a weird kind of way I'm a loner even though I have a family and friends."
Mara Buxbaum, his spokesman, released a statement saying Williams had been struggling with depression in the past few months.
His wife, Susan Schneider, paid tribute to her husband: "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.
"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."
He is survived by son Zak, from his first marriage to Valerie Velardi, and daughter Zelda and youngest son, Cody, from his marriage to Marsha Garces.
The comic, who once said the Kiwi accent sounded like "Australians on Prozac", was a huge All Blacks fan and visited New Zealand in 1999 for the Bicentennial Man film, which he starred in with Kiwi actor Sam Neill.
Before that, he met Jonah Lomu in 1996 and the pair struck up a special friendship. He was often seen wearing an All Blacks cap gifted to him by the former winger.
"He gave me a couple of All Black caps and I wear them around America," Williams said in 1999. "People say, 'What's that team, brother?' and I say, 'The All Blacks', and they go, 'Okay, that's cool'.
"Jonah Lomu's an incredible guy. He just picked me up with one arm."
Following news of Williams' death, Lomu wrote a moving tribute on his website, saying it "was an honour and privilege to have known you".
"You made me laugh even when you weren't even trying to, you were a warm, caring man and funny as hell! Our thoughts are with your friends and family at this time and there is a world of us that will miss you my friend. Till we meet again for more laughs."
Sam Neill also paid his respects - from the set of a movie being filmed in Turkey, the same place he filmed alongside Williams decades ago.
"I am terribly sad to hear this. He was a loveable, kind man, and completely unique."
Williams starred in the movie What Dreams May Come, directed by another Kiwi, Vincent Ward.
In 2010, he performed comedy shows on his Weapons of Self Destruction tour in Auckland and Christchurch, donating the profits from the southern show to Red Cross to help those affected by the 7.1 magnitude September quake. The show was described in the Herald as "madly entertaining".
In the US, television channels broke into scheduled programming to announce Williams' death, and fellow actors and comedians used social media to express their grief.
President Barack Obama also paid tribute to Williams' unique brand of humour.
"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. He gave his immeasurable talent freely and generously to those who needed it most - from our troops stationed abroad to the marginalised on our own streets."
Many of Williams' previous co-stars shared special memories of their time with him throughout yesterday.
Pam Dawber, Williams' co-star in Mork & Mindy, said: "I am completely and totally devastated."
John Travolta, his co-star in the film Old Dogs, said: "I've never known a sweeter, brighter, more considerate person than Robin. Robin's commitment as an artist to lifting our mood and making us happy is compared to none. He loved us all and we loved him back."
Williams, whose battle with addiction involved at least two stints in rehab for drug treatment, posted a photo of himself and his daughter Zelda on his Instagram account two weeks ago for her birthday.
"Happy Birthday to Ms. Zelda Rae Williams! Quarter of a century old today but always my baby girl. Happy Birthday. Love you!" it said.
Zelda yesterday posted an excerpt from French poet and aviator Antoine de Saint-Exupery's El Principito: "You - you alone will have the stars as no one else has them ... In one of the stars I shall be living. In one of them I shall be laughing. And so it will be as if all the stars were laughing, when you look at the sky at night ... You - only you - will have stars that can laugh."
She finished the touching tribute with her own words: "I love you. I miss you. I'll try to keep looking up."
Referring to his off-screen problems, Williams once said: "It [addiction] waits. It lays in wait for the time when you think, 'It's fine now, I'm okay'. Then, the next thing you know, it's not okay."
In the early 1990s he said the death of his friend and the birth of his son prompted him to quit drugs.
In 2006, however, Williams was using again and checked himself in to a substance-abuse rehabilitation centre, later admitting that he was an alcoholic. His relapse into alcoholism, rehabilitation and open-heart surgery were canvassed in an interview with Britain's Guardian newspaper four years ago.
"Oh, God, you find yourself getting emotional. 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.
Asked if he felt happier, Williams replied: "I think so. And not afraid to be unhappy. That's okay too. And then you can be like, all is good. And that is the thing, that is the gift."
Where to get help
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (4pm to 6pm weekdays)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• The Word
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
