‘Iwas 11 when I started selling drugs. I thought it was candy.” A young man in Mexico City is talking about his initiation into a drugs gang and is one of a handful of young Mexicans interviewed in this documentary about gangs and gun violence. They tell their stories softly on voiceover, reflective and raw, without swagger or machismo. It’s a million miles from the cartel bad-guy stereotypes of Hollywood narco movies. And the more they talk, the thinner the line between victim and perpetrator becomes. The film’s title is a bit confusing. Ernesto is a collective name given by director Everardo González to the men he interviews to protect their anonymity. They appear with faces hidden, filmed from behind using iPhones attached to their backs: the effect is like a first-person shooter game. It’s disorienting at first, and the men’s stories blur into each other. Which is presumably González’s point: there’s a pattern. These young men were not born dangerous. Aged nine or 10, the grooming began; a guy from a gang takes an interest, plays computer games with the kid, asks how he’s doing. By the time the kid is a teenager, high as a kite on solvents and alcohol, armed with a gun, he is ready to kill. “Under the influence everything is easier,” one puts it. It’s almost impossible to get out of the gang; they own you. The end of the story is usually the same: “You die.” But it’s not just men; the film also follows two women involved in gangs. One of them rents out guns by the hour ($12 for one hour; $25 for four); she started after splitting up with the father of her kids. A major supplier of guns is the police: officers take them from criminals one day only to sell them back to the streets. This is a revealing, troubling film. A Wolfpack Called Ernesto is in UK cinemas from 23 February.