David Ayer, the writer of Training Day, director of Street Kings, writer/director of Harsh Times, does not make movies about princesses with witchy curses, about yuppie commitment-phobes, about talking plush toys.

His territory is narrow, but he owns it: cops, in Los Angeles.

And in End of Watch, with Jake Gyllenhaal and Michael Peña as officers on patrol in one of the nastier quadrants of South Central L.A., Ayer delivers a film of extraordinary fire power, literally (AK-47s! Glocks! Smith & Wessons!) and figuratively. Deploying all manner of cameras - microcams that hook on shirt pockets, dashboarded-mounted cams, cellphone cams, webcams, surveillance cams, HD camcorders - Ayer follows officers Brian Taylor (Gyllenhaal) and Mike Zavala (Peña) as they investigate domestic disturbances, respond to complaints of raucous late-night parties, make traffic stops, and rescue babies from burning houses.

All in a day's work - work that they love - until they pull over a pickup truck, discover a cache of guns and bags of cash, and then make an even more momentous find at a house in the barrio.

"You just tugged on the tail of a snake," a federal agent warns Taylor, the G-men in bullet-proof jackets swooping down on the two LAPD uniforms. "It's going to turn around and bite you back."

Visceral and violent, but anchored in the humanity of its two leads, End of Watch feels more real than reality TV (which isn't saying that much, I guess), but boasts the pulse-pounding thrills of slicker Hollywood cop pics, too. The auto-documentation gimmick comes by way of Gyllenhaal's character - Taylor is in grad school, taking a course in moviemaking, and so he has decided to record his experiences as a beat cop, poking his camera around the precinct locker room, letting it run during roll call, taking it onto the street. His superiors don't like the idea, and he's leaving himself open for all sorts of litigation, but he does it anyway. Taylor is like that - cocky.

He and Zavala are best friends, and as they cruise around, stopping in corner bodegas, making vehicle checks, they talk about their hopes, their plans, their dreams. Zavala is married to his highschool sweetheart (Natalie Martinez), and she's about to have a baby. Taylor is tired of the rituals and rigors of dating and is looking for a serious relationship - and thinks he has found one in a girl he first meets at a Starbucks, Janet (Anna Kendrick).

Things are looking good for Taylor and Zavala, their bond is strong, they have each other's back - and then a Southland street gang tied in with a Mexican drug cartel gets its marching orders.

End of Watch has its flaws. The "hoodrats and homies," with names like La La, Demon and Big Evil, can come off as cartoonish, and the raw honesty of the film is compromised by the knee-jerk mechanisms of, if not a happy ending, a happier ending than the terrifying climactic shootout dictates.

But End of Watch is powerful, and Gyllenhaal and Peña, who trained for months for their roles, display the moves, and mentality, of dedicated police officers. It's not a pretty job. But it's a pretty awesome film.