Director Gus Van Sant has said he based his latest film on the 1999 Columbine school shootings to "capture the atmosphere of the event".
Van Sant's film, Elephant, is up for the Palme d'Or prize at Cannes Film Festival and observes the highs and lows of school life for teenagers in the build-up to the fatal shootings.
The director said he wanted to make "a movie that dealt with the characters in the story of the event".
The director and cast are in Cannes promoting the film
The 1999 school shootings in Colorado, US, horrified America when two teenagers killed 12 pupils and a teacher before shooting themselves.
After the events at Columbine there was an "upswell of concern and sanctions against violence", said Van Sant, who is famed for directing Good Will Hunting and My Own Private Idaho.
"American shootings had reached an all-time high by 1999", he said, although he stressed he did not want his film to try to explain why they had happened.
This contrasts with Michael Moore's Oscar-winning documentary Bowling For Columbine, which explored US gun culture and won a special prize at Cannes last year.
Van Sant said he thought Moore's film was "brilliant", but added: "We didn't want to explain anything. As soon as you explain one thing, there are five other possibilities that are somehow negated because you explained it one way.
"There was also the issue of finding an explanation for something that doesn't necessarily have an explanation."
The film is set in a US high school
Although Van Sant's film does not flinch from portraying the shootings, it also explores the everyday lives of the students and their experiences at school.
"For some of them it's very hard to be in school, it's like hell. For others, school is great," he said.
"I think there was a similar disparity when I went to high school."
Three of the actors in the film, who attended an open audition of 3,000 teenagers, said the real-life shootings had had a big effect on their lives.
"It had an impact on all kids in the US," said John Robinson, who plays one of the children who survived.
"But being in the film has put pressure on us to become spokesmen for kids in the US."
Alex Frost, who plays one of the armed teenagers, added: "It changed how we were in school, how we all acted."
Alex Frost's character has deadly ambitions
And Elias McConnell, who plays a student interested in photography, added: "I wasn't affected in the same way because I'm home-schooled. But it scared me and made me happy I don't go to high school."
Colin Callander, president of HBO Films, which backed the movie, said detail on how the youngsters got hold of the guns was deliberately vague, as it would be "utterly irresponsible" to show how weapons could be acquired.
The film's title is taken from a 35-minute documentary in 1989 by the late British film maker Alan Clarke, in which it depicts Northern Ireland's sectarian violence as "a relentless anonymous march of murders".
Clarke took his title from a saying about the "elephant in the living room", meaning an issue no one wants to talk about or acknowledge.
Actress and director Diane Keaton, who was one of the film's executive producers, spoke recently of the effect the film had on her.
"It really makes me think about my responsibilities as an adult to try and understand what's going on with young people," she said.
"What's striking is it's such a pure piece. Gus didn't try to make it anything other than what he felt high school is for some young adults.
"You experience what it's like for them."