Robin Williams appeared to have hanged himself with a belt and cut his wrist before being found by his assistant, authorities said Tuesday.

Williams was discovered with a belt wrapped around his neck, wedged between a closed closet door and door frame, said Lt. Keith Boyd, assistant chief deputy coroner with the Marin County Sheriff's Office.

"His right shoulder area was touching the door," Boyd said.

Williams was also found with several "acute, superficial" cuts on the inside of his left wrist, Boyd said.

A pocket knife with a closed blade was located near his body with what appeared to be dried blood on it, he said. It was not immediately clear how many wounds Williams had.

"He was slightly suspended in a seated position," Boyd said. "Unfortunately we still have to surmise ... to try to come up with a generalized idea of when he passed."

Williams was found clothed, he said, by his assistant late Monday morning.

Authorities will perform a toxicology report, Boyd said, which will take several weeks for the results.

A day after his death shocked the country, new details emerged about the extent of Williams' battles with depression and drugs. For years, Williams struggled with alcohol and drug addiction, most recently checking himself in to a Minnesota facility in July.

The renowned funnyman had recently been coping with depression, said his representative, Mara Buxbaum, in a statement on Monday.

His wife, Susan Schneider, was the last person to see Williams alive before she went to bed at about 10:30 p.m. on Sunday, Boyd said. Williams then went into a separate bedroom inside the Tiburon home, just north of San Francisco.

At about 10:30 a.m. on Monday, Schneider left home "believing Mr. Williams to still be asleep," Boyd said.

Williams' personal assistant then "became concerned" at about 11:45 a.m. when the actor didn't respond to persistent knocking on the bedroom door. The assistant was able to gain access to the bedroom, Boyd said, where he found Williams' body.

It's unclear exactly what time Williams went into the room, Boyd said. Boyd declined to comment on whether Williams left a suicide note.

Schneider said she'd remember her late husband by 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," Schneider said in a statement. "I am utterly heartbroken."

Williams' daughter, actress Zelda Williams, on Monday night tweeted a quote from Antoine De Saint-Exupery and wrote "I love you. I miss you. I'll try to keep looking up. Z."

On July 31, Williams posted a photo of him and his daughter on Instagram from several years ago -- the last post he made.

There has been an outpouring of sadness and support from Williams' Hollywood colleagues, politicians and fans alike.

President Barack Obama offered heartfelt condolences to Williams' friends, family and "and everyone who found their voice and their verse thanks to Robin Williams" following news of his death. Williams "gave his immeasurable talent freely and generously," Obama added.

"Robin Williams was an airman, a doctor, a genie, a nanny, a president, a professor, a bangarang Peter Pan, and everything in between," Obama said in a statement Monday. "But 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."

The Academy of Motion Picture Arts & Sciences posted a photo of one of Williams' memorable roles as the genie who wished for freedom in "Aladdin."

"Genie, you're free," they wrote.