The Castro Theatre was packed with a sold-out crowd last night for the world premiere of "Q Ball," a new documentary executive-produced by Golden State Warriors star Kevin Durant.

The film is about a different Warriors team — comprised of inmates at San Quentin State Prison (colloquially known as "The Q") in Marin County. It follows two members of the team on their personal journeys to rehabilitation, as well as the team's head coach, a convicted murderer who works to prepare players for their return to the outside world. 

Part of Fox Sports' "Magnify" series of feature-length documentaries, "Q Ball" is set to air on the network later this year. 

While the documentary is mostly set inside San Quentin, it also captures San Francisco neighborhoods like the Mission and North Beach, where some of the inmates involved in the basketball program were born and raised.

The film's director, Bay Area-based Michael Tolajian, has deep experience in making films about basketball's effect on the wider world. He previously directed the ESPN "30 For 30" documentary "Once Brothers," about two players on the Yugoslavian national basketball team who became best friends and made it to the NBA, only to see their relationship destroyed by the Yugoslavian civil war.

He also directed the 2013 feature "Bluegrass Kingdom," about the University of Kentucky's popular college basketball program. 

Tolajian feels the project is important for Bay Area locals, especially since San Quentin remains "an infamous place" due to the legacy of inmates like Charles Manson, he said.

He hopes that the documentary will show how San Quentin has transitioned to become more progressive, with a number of volunteers and programs to help inmates who've accepted what they’ve done and want to change and become better men.

Tolajian said that Durant has been a key asset to the project, helping to kickstart it and get it on the map with Fox Sports.

“When he visited San Quentin, he was impacted by that visit," he said. "Ever since then, he’s been super supportive in making the film. He’s never one to force his hand — he’s just been there for support and guidance."

To avoid crowds of fans awaiting his arrival, Durant made a brief appearance just after the lights went down, slipping into the theatre after the movie had started and leaving before the post-screening Q&A. He briefly posed for official media photos as well. 

Tolajian said he's proud to have premiered "Q Ball" in the Castro.

“I could not pick a better time and better venue to show this film," he said. "It’s a local story. A lot of the subjects in the film are from this area, and this is an iconic venue.”