On Monday night, HBO premiered the Sundance documentary “Valentine Road,” about the brutal murder of 15-year-old Lawrence King from Oxnard, Calif.

King, who came out of the closet at the age of 10, started to show up for the eighth grade at E.O. Green Junior High School in women’s makeup and stilettos, and he embarrassed classmate Brandon McInerney at lunch by asking him to be his valentine. On Feb. 12, 2008, McInerney sneaked a gun to school and shot King in their first-period English computer lab.

After the shooting, the district attorney’s office charged McInerney, who was 14 at the time, as an adult and of a hate crime, which brought a flurry of media attention to this blue-collar town outside Los Angeles. I was among the early journalists on the scene, and I spent five months there reporting an investigative cover story for Newsweek that explored the complicated events leading to King’s murder.

Both King and McInernary came from troubled childhoods and they often acted out at school. At the time of his death, King was living in a group home after he had been removed from his adopted parent’s care. Dawn Boldrin, the teacher who had both boys in English class that day, and had previously given Larry a green dress as a present, eventually left her job.

First-time director Marta Cunningham spent four years working on “Valentine Road” and collected 350 hours of footage. She interviewed some of King’s friends and McInerney’s family, but she wasn’t able to get inside the school or talk to the district superintendent, Jerry Dannenberg. Still, she hopes other classrooms will show her film as an educational tool. She spoke to me about the Oxnard murder earlier this week.

Ramin Setoodeh: I wanted to have a conversation because this story has been important to both of us for a long time. I remember receiving a voicemail from you in 2008, after you had read my article in Newsweek.

Marta Cunningham: I first started off with the idea of doing a short film about the incident itself. I started talking to the kids, and I sat in hearings and I realized this was a documentary and not a short narrative film.

RS: You had never made a film before. How did you get started?

MC: I think I just wanted to do it. I hired the right people and did a ton of research. I had been an actor for probably 15 years. So I was really comfortable in that regard of what a director’s job is and what a producer needs to do.

RS: How did you pay for it? Did you finance it yourself?

MC: At first, we were financing it. Then we had fundraisers and put together a sizzle reel. Someone said I need to get it to [documentary producer] Eddie Schmidt, because he will really love this story.

RS: For me, the hardest part about doing the story with kids so young was separating what they had heard from friends versus what they had witnessed themselves. Was that a challenge for you?

MC: I think the two children that take us through the story are Marina and Mariah, and they were witnesses to the actual crime. And they take us through their journey. I think that was the main [arc] of the film. And the kids that are kind of on the outskirts of the story, really we had them talking about their experiences that day.

RS: One of the things that was surprising for me at the school—

MC: Oh, they wouldn’t talk to me.

RS: I went on campus and talked to the teachers. After two teachers complained to the administration that Larry was disrupting instruction with his wardrobe, there was an email sent to the staff that said Larry was allowed to dress how he wanted.

MC: There needed to be a lot of guidance that wasn’t provided to anyone in the school.

RS: The teachers also said that Larry had been sexually harassing some of the male students at school, including Brandon.

MC: Well, the people I talked to, the kids I talked to, none of them commented on that. That wasn’t anything they told me about. It wasn’t something I purposefully left out. The only thing I heard, when it came to any kind of sexual harassment, was from the defense team.

RS: Do you think Brandon should have been tried as an adult?

MC: No.

RS: Do you think it was a hate crime?

MC: I do think it was a hate crime. I always thought it was a hate crime. I think he was motivated by that. There was never one part of me that wavered from that. A lot of it has to do with the family life he had and who he was hanging out with. From what Kendra [Brandon’s mom] told me, she has a lot of regret about the amount of hatred Brandon was around when it came to Billy [Brandon’s now deceased father]. And how he referred to any derogatory term that he could think of. I think when you’re raised with that level of hatred, it adds up.

RS: Why didn’t the first jury reach a verdict? [Brandon later pleaded guilty to second-degree murder, and he was sentenced to 21 years in prison.]

MC: They say it in the film. They saw him as a child. They didn’t want to put a child in prison for 53 years to life without a chance at parole. They also didn’t think it was a hate crime. Not one juror thought it was a hate crime. They didn’t believe it — they didn’t believe he was a white supremacist or racist to that degree.

RS: Was this an emotional story for you? It was for me.

MC: It was an emotional roller coaster.

RS: What stayed with you most from Larry’s story?

MC: Going to the graveyard. I think the last day, a butterfly flew by in the shot. It was really magical.