Ethan Hawke was only a teen when he co-starred with Robin Williams in 1989’s Dead Poets Society, but he could sense the comic actor’s epic battle with depression. “With great highs come great lows,” Ethan said at the recent Montclair Film Festival in New Jersey. “Robin was amazing, funny, brilliant, silly, and really sad sometimes. So sad. A sadness that had gravitational pull. It would alter a room.”

Now two new profiles — the just-released biography Robin and Marina Zenovich’s documentary Robin Williams: Come Inside My Mind (airing on HBO in July) — offer new insight into the struggles that ultimately led the funnyman to take his own life at 63 in 2014. “He was a joyous spirit that people loved and trusted,” says best friend Billy Crystal. “My heart breaks that he suffered and saw only one way out.”

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The roots of Robin’s loneliness ran deep. He spent much of his childhood alone, and his family moved frequently; his distant dad worked for Ford Motor Co. and traveled often. One night, “I saw my father watching The Tonight Show with Jonathan Winters,” Robin recalled. “My dad lost it, and I said, ‘Who is this guy that made the great white father laugh?'”

Robin saw comedy as a way to find love and wed Valerie Velardi in 1978, the same year he achieved superstardom with his manic shtick on Mork & Mindy. “We were having an adventure, then everything changed,” Valerie says. “He loved women. I understood that. But I also wanted him to come home.” Infidelity drove Robin and Valerie apart, and they had been separate for a year when he began to date Marsha Garces, who’d breifly worked as his son Zak’s nany. Robin and Marsha “got skewered” in the press, says Valerie. “I’m sorry Marsha had to start her adventure with Robin in such an unpleasant way.”

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Still, Robin and Marsha married in 1989 and had two kids, Zelda and Cody. “My life was saved by her, not ruined by her,” Robin said. But Robin — who’d been scared sober after pal John Belushi OD’d hours after they’d partied together in 1982 — fell off the wagon while shooting the 2005 movie The Big White in a remote Alaska location. By 2010, Robin and Marsha had divorced.

A year later, he got remarried to Susan Schneider. Soon, health problems overwhelmed him. “His body was stiff, and he wasn’t super-sharp — he looked like a wax figure,” says Mork & Mindy’s Pam Dawber, who guested on Robin’s short-lived sitcom, The Crazy Ones, in 2014. “He wasn’t the happy soul he’d been.” Afflicted with undiagnosed Lewy body dementia, Robin was living what he’d called his worst nightmare: “becoming dull…a rock…I couldn’t spark.” His quicksilver wit, long Robin’s shield, was gone. As Ethan put it, “Robin was like Don Quixote, battling those windmills. And he just got tired.” But what a legacy of laughter he left behind.

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