U.S. President Barack Obama today led the outpouring of sympathy messages for the death of veteran actor and comic Robin Williams, who was found lifeless Monday in his home in Tiburon, California, just north of San Francisco. Williams was 63.

In a touching tribute from the White House, President Obama referred to Robin Williams as "an airman, a doctor, a genie, a nanny, a president, a professor, a bangarang Peter Pan, and everything in between."

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"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 marginalized on our own streets," the President said.

Obama also offered his family's condolences "to Robin's family, his friends, and everyone who found their voice and their verse, thanks to Robin Williams."

The Marin County's Sheriff's Office is set to make a statement before the press around noon Tuesday about the cause of Williams' death, although authorities hinted earlier they suspect is was an apparent suicide due to asphyxia.

Williams has had bouts of depression, and in July was undergoing a 12-step treatment program while staying in a "Minnesota facility," said his publicist Mara BuxBaum.

The actor himself had been candid about the challenges of maintaining sobriety. He had sought treatment in 2006 when he relapsed and returned to drinking after 20 years.

Among Williams' friends who have given their statements include Gleen Close who co-starred with him in "The World According to Garp."

"I am absolutely heartbroken. Robin was a national treasure and a beautiful soul. My deepest sympathy goes to all his family," Ms. Close said.

Actress Mara Wilson, who was six years old when she starred with Williams in the movie "Mrs. Doubtfire," was one of the first to learn about the death and tweeted this message: "Very sad, very upset, very glad I did not have to hear about this though Twitter. Probably going to be taking some time off it for a while." 
 
Author John Green tweeted this message about William's death: "Very sad to hear that the brilliant comedian and actor Robin Williams has died at 63. Williams had a wonderful gift for helping us to glimpse the horror and humor deep inside of others and ourselves."
 
Sympathizers have been leaving flowers, candles, and messages on his star at the Hollywood Boulevard Walk of Fame and outside his home in Tiburon.