"You're only given a little spark of madness, and if you lose that, you're nothing," the late actor and comedian Robin Williams says in an interview resurfaced for HBO's upcoming documentary about his life.
The cable network released a sneak peek on Thursday of "Robin Williams: Come Inside My Mind," a film produced by Alex Gibney and Shirel Kozak that hits the small screen on July 16.
The documentary uses interviews with Williams, who died by suicide in August 2014, to paint an intimate portrait of one of America's greatest entertainers. The trailer features the actor's son Zak Williams and comedy giants including Steve Martin and Billy Crystal sharing their memories.
"My father didn't always feel he was succeeding, but he was the most successful person I know," Zak Williams says.
The comedian's widow, Susan Williams, told People magazine in 2015 that an autopsy revealed her husband had a progressive brain disease called diffuse Lewy body dementia, or dementia with Lewy bodies. The complex disease is the third most common cause of dementia, with the symptoms worsening over time. Susan Williams said her husband experienced unexplained mental symptoms during the year of his death.
Watch the trailer above.