HBO’s Oct. 3 screening of “Valentine Road” caused a major commotion — as in audience members’ heckling the screen in disbelief. Throughout the 90-minute film about the 2008 murder of transgender eighth-grade student, Lawrence “Larry” King, a steady stream of  “No!” and “Are you kidding me?” filled the intimate screening room at HBO’s headquarters.

First-time filmmaker Marta Cunningham told the audience post-screening that “this film is a lot to take in. There are  so many youth (in this country) who are invisible. I’m glad that you witnessed it. This is a film, but it’s also a call to action.”

Helmer, who was on crutches due to a recent fall, said that she began filming just six months after Larry’s death. She gained unprecedented access using a bit of TLC.

“The kids (in Larry’s class) really needed someone to talk to,” she said. “The fact that I cared and they could tell that I cared was big. No one in the school was really there for them. So getting a hug was a huge deal.”

Producer Sasha Alpert said that she was attracted to the project, which premiered at Sundance, due in part to the honest nature of youth.

“There is something about their honesty that draws you in,” she explained.

Cunningham said she made the film, which raises urgent issues about the safety of LGBT teens, juvenile justice and the efficacy of the country’s educational and social service systems, mainly because she believed that Larry’s untimely death was forgotten too quickly.

“It was such a tragedy not being  talked about in the national media to the degree I thought it should be.”