Robin Williams' Son and Billy Crystal Recall Actor's Decline: 'I Never Heard Him Afraid Like That Before'

The two shared some of their final interactions with the late, legendary actor in excerpts from Dave Itzkoff's upcoming biography, "Robin."

In the passages released in Vanity Fair, Crystal recalled the moment where his former friend first informed him of his Parkinson's disease diagnosis shortly before his death in August 2014. "I never heard him afraid like that before," he said. "This was the boldest comedian I ever met - the boldest artist I ever met. But this was just a scared man."

An autopsy later found that Williams actually suffered from Lewy body dementia, a brain disorder with symptoms including depression and hallucinations.

Crystal began to notice changes in his friend's personality over a year before the diagnosis, however. "He wasn't feeling well, but he didn't let on to me all that was going on," Crystal recalled. "As he would say to me, 'I'm a little crispy.' I didn't know what was happening, except he wasn't happy."

The actor went on to detail a double date he and wife Janice had with Robin and his wife Susan in 2013. "I hadn't seen him in about four or five months at the time," Crystal explained. "And when he got out of the car I was a little taken aback by how he looked. He was thinner and he seemed a little frail."

"He seemed quiet. On occasion, he'd just reach out and hold my shoulder and look at me like he wanted to say something." At the end of the night, Williams showed Crystal and his wife an unusual burst of emotion. "He hugged me goodbye, and Janice, and he started crying," Crystal said. "I said, 'What's the matter?' He said, 'Oh, I'm just so happy to see you. It's been too long. You know I love you.'" He followed his goodbye up with a number of phone calls where he expressed his love for the duo, before asking, "Did I get too sappy?"

"It was really difficult to see someone suffering so silently," his son Zak added. "But I think that there were a series of things that stacked, that led to an environment that he felt was one of pain, internal anguish, and one that he couldn't get out of. And the challenge in engaging with him when he was in that mind-set was that he could be soothed, but it's really hard when you then go back into an environment of isolation. Isolation is not good for Dad and people like him. It's actually terrible."

Zak also revealed that his father felt a sense of guilt over divorcing Marsha Garces -- the mother of his two siblings -- no matter how hard they tried to reassure him it was OK.

"He couldn't hear it," Zak recalled. "He could never hear it. And he wasn't able to accept it. He was firm in his conviction that he was letting us down. And that was sad because we all loved him so much and just wanted him to be happy."

Williams took his own life at the age of 63 in 2014. "Robin" goes on sale May 15.