"Stand-up is survival," says Williams at the beginning of the clip as behind-the-scenes photos of him appear on the screen. "For me, that's jazz—that's what I have to do."
The trailer proceeds to show several friends and family sharing their thoughts on the late comedian. He was "like nothing I'd ever seen," says comedian Lewis Black.
"He was really comfortable onstage," Steve Martin adds later on before sharing a disheartening observation.
"Offstage, I just felt he was holding himself together," Williams' son Zak is also featured in the clip. "My father didn't always feel he was succeeding. But he was the most successful person I know."
The trailer also features photos of Williams and footage from his stand-up routines. There are also interviews with Williams which adds an intimate aspect of the late comedian's words.
Then, it ends as it begins: with Williams' voice. "You're only given a little spark of madness and if you lose that, you're nothing," he says.
Williams died from suicide in 2014. The documentary will explore his life and career until his untimely death.
HBO's Robin Williams: Come Inside My Mind, which also reportedly features Eric Idle, Whoopi Goldberg, David Letterman and Pam Dawber, is scheduled to air on July 16.
If you or someone you know is in crisis and needs help, call the National Suicide Prevention Lifeline at 1-800-273-8255.