Police believe Williams, 63, known for films such as Good Morning Vietnam and Mrs Doubtfire, took his own life on Monday.A representative for the actor said he had been battling severe depression recently.In a statement his wife, Susan Schneider, said she was "utterly heartbroken"."On behalf of Robin's family, we are asking for privacy during our time of profound grief," she said."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."This morning, I lost my husband and my best friend, while the world lost one of its most beloved artists and beautiful human beings.Robin Williams’ wife, Susan SchneiderIn a tribute on Twitter, his daughter Zelda, who recently celebrated her 25th birthday, posted an excerpt from French poet and aviator Antoine de Saint-Exupery's El Principito along with the words "I love you. I miss you. I'll try to keep looking up".Mara Buxbaum, Williams' press representative, said: "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."In a statement, Marin County Sheriff's Office added: "A comprehensive investigation must be completed before a final determination is made."It said that an investigation into the "cause, manner, and circumstances of the death is currently under way".The actor was pronounced dead at 12.02pm local time, the sheriff's office confirmed.A forensic examination is expected to take place later before toxicology tests are carried out.Robin Williams tributesWilliams shot to fame in the late 1970s. He won an Oscar in 1998 for his role in Good Will Hunting.US president Barack Obama led tributes to the star as a host of Hollywood A-listers spoke of their shock at his death.Fellow comic Steve Martin, who appeared alongside Williams in a 1988 theatre production of Waiting for Godot, said: "I could not be more stunned by the loss of Robin Williams, mensch, great talent, acting partner, genuine soul."Others who paid included Kevin Spacey, who was in the 2009 film Shrink alongside Williams and actress Mara Wilson, who played Williams' daughter in Mrs Doubtfire.