David Steinberg, executive producer of “Robin Williams: Come Inside My Mind” and longtime manager to Williams, watched the legendary comedian perform countless shows over the years. But one memory that sticks out occurred while his client was on a United Service Organizations tour, where Williams performed standup for hundreds of wounded servicemen and women before personally greeting each of them.

“Someone who could do that can certainly mask some of what’s going on inside of him,” Steinberg told Variety.

On the red carpet for Wednesday’s premiere of HBO’s Williams documentary at the TCL Chinese Theatre in Hollywood, filmmakers, actors and comedians shared their on-screen and off-screen memories of Williams, who died by suicide in 2014.

Though nearly four years have passed since Williams’ death, mental health has been a widely discussed topic in recent weeks following the suicides of fashion designer Kate Spade and cooking personality Anthony Bourdain. In light of their deaths, Steinberg and others in attendance discussed the topic of mental health.

“I think the problem is that pain is so deep-seeded — it doesn’t reveal itself,” Steinberg said. “The curtain’s closed on that part of the head, and I can’t imagine. I have theories, but I’m not a doctor. I think everybody’s just got to be open, understanding and encouraging to people who reveal who they are … What can we do? Listen to people.”

Comedian Eddie Griffin said mental instability is “par for the course” of a comic, who makes a living by appealing to strangers’ emotions.

“Being a comedian — a true comedian — you’re hypersensitive,” Griffin said. “You care enough to see sadness in people and want to bring laughter and joy to them. But is there anybody there to bring laughter and joy to the comedian?”

Marina Zenovich, who directed the documentary, said she hopes viewers come away from the documentary with a greater understanding of who Williams was, as well as his internal demons. While making the film, Zenovich, who had been a fan of Williams’ professional work since “Mork and Mindy,” was surprised to hear many of her subjects describe a quiet and introspective side of Williams that audiences never saw.

“I don’t think he was himself when he [died] — I don’t think he knew what he was doing,” Zenovich said. “The whole point is to get help before they get to that point, so if this film can, in any way, help, that would be amazing. I don’t know if it can, but I hope so.”

Both Zenovich and Griffin added that they would like mental illness to be de-stigmatized in order to facilitate more productive discussions around how to seek help without “shame.”

“Mental health shouldn’t be looked at in an ugly light,” Griffin said. “It should be like any other sickness — like cancer, like HIV, anything else. There’s got to be compassion and the ability to step out of your own ego and put yourself in somebody else’s shoes.”

Williams’ longtime comedy partner and documentary film subject Billy Crystal acknowledged the pain that lives inside many, but urged audience members to shed that negativity in honor of the night’s late star.

“We’re coming up to four years without him,” Crystal said ahead of the screening. “The world is a darker and lonelier place for a lot of us, for a lot of reasons. So tonight, when you watch this film, rejoice in the fact that you had him for as long as you did. Rejoice in the fact that you witnessed some really amazing comedy, some brilliant receptions, and he broke your heart in the same way as an actor. And rejoice in that fact that you get a chance to go inside Robin Williams’ mind.”

Others in the premiere’s attendance included producer Shirel Kozak, Bob Einstein, Brad Garrett, Ray Romano and Bob Saget.

“Robin Williams: Come Inside My Mind” debuts July 16 on HBO.