PARK CITY, Utah -- Talk about unlikely film follow-ups. The feature documentary "Made in America," which premiered at the Sundance Film Festival this week, is probably the last thing you'd expect from director Stacy Peralta.

The former golden boy, skateboard-manufacturing mogul turned filmmaker doesn't seem like a natural candidate to make an unflinching documentary about four decades of gang warfare between the Crips and the Bloods. In order to shoot it, Peralta had to brave South Los Angeles' most dangerous neighborhoods, interview people with pistols in their waistbands and cozy up to local "shot callers" in order to get his "pass" -- the 'hood version of a location permit.

But by turning his camera on Los Angeles' most lethal street gangs, the West L.A.-born director, one of skateboarding's earliest professionals, says he has completed another chapter in his Angeleno documentary movie "trilogy" while also trying to expose a social malady with deep roots in the City of Angels.

"I'm an L.A. boy. All the stories we've told are L.A.-centric," said Peralta, 51, whose "Dogtown & Z-Boys" chronicles a pioneering '70s skateboard team from Santa Monica that basically invented extreme sports, and whose second movie documentary, "Riding Giants," provides an oral history of surfing. Both films also premiered at Sundance.

"And put it this way," Peralta continued, seated in a coffee shop, "if white American teenagers were forming gangs, arming themselves with assault rifles and killing each other, what do you suppose the response of the U.S. government would be? It would be over in a day. This has been going on for 40 years. So this film was an opportunity to explore this and find the human face behind it."

Some people in the audience of the film's first public screening Sunday were moved to tears by "Made in America's" hard-hitting message -- that gang warfare in Los Angeles is, for all intents and purposes, a "civil war."

To support this thesis, the film traces the evolution of gangs from all-black "social clubs" based in public parks in the '60s, through the empowering effect of the Watts riots in 1965, charting the rise of the civil rights movement through the death and imprisonment of its most able leaders. Los Angeles' grid of freeways is also shown as promoting segregation and institutional racism by creating psychological barriers between blacks and whites (with borders that were for many years physically enforced by police).

Add to that South Los Angeles' chronic joblessness, hopelessness and crack epidemic and, the film argues, the stage is set for young blacks to turn against one another rather than rage, together, against the proverbial machine.

Even more poignantly, "Made in America" posits that Los Angeles' gang strife has lasted longer and claimed more lives than the so-called Troubles in Northern Ireland and resulted in a higher incidence of post-traumatic stress disorder among the children in South L.A. than among those in Baghdad.

"Because they're poor black youth, these kids don't rate high enough for it to be called a civil war," Peralta said. "They don't have enough value placed on them. The message is: 'You're not worth it.' "

Tough talk indeed -- worthy of Peralta's stated ambition of changing public attitudes and challenging governmental policies concerning gangs in L.A. But many a documentarian has tread perilously close to sensationalizing his story subjects while trying to make a strong point. And at times, "Made in America's" social agenda is more than a little conspicuous. Asked if the filmmakers had overstated their case, however, community activist Kumasi -- a member of one of L.A.'s original street gangs who is interviewed in the film -- voiced support for Peralta's editorial choice.

"Every country has been torn to pieces by civil war and then reconstructed itself," Kumasi said. "The people in this country realize how detrimental one can be. So I like the language he used because it can make people have the same consideration when they're thinking about this neglected part of society inside this country. They weren't sensationalizing this cult of death."

Paradoxically, while trying to frame the debate about South L.A.'s internecine warfare, production on the film helped broker a fragile peace between gang factions. Clifford "Skipp" Townsend, an inactive member of the Rollin' 20s Bloods, who is interviewed and served as a consultant on the movie, recalled filming a segment surrounded by people with whom he ordinarily -- and literally -- wouldn't have been caught dead.

"One time, Stacy had guys who had shot at each other, guys who had been enemies, sitting on the same porch," Townsend said. "It was powerful and uplifting to learn about these people I thought were totally different from me. One of those guys was killed later."

Ultimately, the filmmakers granted their subjects an unusual amount of creative control. Peralta and his producers (Golden State Warriors point guard Baron Davis and Jesse Dylan, son of Bob, among them) screened early cuts for gang members, soliciting feedback and rejiggering the ending to conclude on a more optimistic note by showing reformed gangsters making a difference in their communities.

"We weren't going to finish this thing unless these guys blessed it," Peralta said.

"In the first screening, there was no mention of the positive aspects of what's going on now," Townsend said. "The first [cut of the] film was more the gruesomeness, the animalistic behavior."

"Made in America's" penultimate scene involves a montage of mothers whose children were lost to gang violence. They stare wordlessly at the camera, some crying. The footage hit home for Rodney "Shaka" Moralez, a member of the Family Swan Bloods, who was interviewed in the film and saw it for the first time at Sundance.

"It touched me because a lot of the time, when you're gang banging, you don't see the aftermath of the destruction," Moralez said. "It made me feel angry with myself. I felt the pain those mothers were going through. I possibly made other mothers feel the same grief and pain."

He paused, then added: "It's important for us to deal with the anger that's building up inside us because if we don't, we're going to destroy our communities, our families. Ourselves."