The debut trailer for the new HBORobin Williams’documentary teases an intimate look at the beloved comedian during his best and darkest hours.

While interviews with contemporaries like Billy Crystal, Eric Idle, Whoopi Goldberg, David Letterman and Steve Martin, along with family members like his son, Zachary, provide commentary on Williams’ career, the documentary is told largely through previously recorded interviews with the actor himself.

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Robin Williams

Despite growing up wealthy — his mother was a model and his father was a Ford Motor Company executive — Williams spent most of his childhood feeling painfully shy. Often retreating into his own world of pretend and solitude, playing with toy armies in the basement of his family’s mansion, Williams didn’t view his parents as being particularly warm. “The ideal child was seen, not heard,” Williamstold PEOPLEin 2009.

Even after finding solace onstage as a performer, Williams was never fully able to enjoy the fruits of his labor. “My father didn’t always feel he was succeeding, but he was the most successful person I know,” his son Zachary said in the trailer.

In an interview with PEOPLE shortly after her husband’s death, Susan Williams opened up about her his struggle with the debilitating brain disease, which had begun taking its toll on the actor in the last year before his death.

Susan explained that although in the months leading up to his death, her husband’s symptoms — which includedheightened levels of anxiety, delusions and impaired movement— worsened, doctors weren’t able to make the diagnosis until they performed the actor’s autopsy.

“I know now the doctors, the whole team was doing exactly the right things,” Susan continued. “It’s just that this disease was faster than us and bigger than us. We would have gotten there eventually.”

source: people.com