David Ayer's gritty, humorous and moving film stars Jake Gyllenhaal and Michael Pena as police officers on the beat in South-Central L.A.

From the first tires-squealing, sirens-blaring, guns-blazing car chase to the last quiet conversation, "End of Watch" is a visceral story of beat cops that is rare in its sensitivity, rash in its violence and raw in its humor.

For David Ayer, who has long made the minefield of police work his metier, this blood-drenched and unexpectedly moving film is his best cut yet on what life is like on that thin blue line. Jake Gyllenhaal and Michael Peña star as partners fighting crime on the streets of South-Central Los Angeles. Their beat is poverty riddled and gang infested. Drug running, turf wars and lethal grudges that only end badly frame their days. It's all captured with a gritty hand-held intensity that keeps you on edge and unsettled, waiting for the next shoe to drop.

The story is, in a way, an ordinary one — regular cops who aren't corrupt, guys who chalk up any heroics to just doing their job. In a reflection of reality, much of the film is spent with officers Brian Taylor (Gyllenhaal) and Mike Zavala (Peña) in their squad car. The age of cellphone videos has imprinted the film's style. At times they feel barely an arm's length away.

No single bad guy emerges, no one case has to be solved. Instead the film's rhythm is set by the day-in and day-out routine of police work. Ayer has done a solid job of keeping Brian and Mike rocking between boredom and adrenaline-pumping action, starting with Sarge (Frank Grillo), whose admonishments begin their shift, to the streets where they never know what will happen and finally to the paperwork at end of watch. The crime is of the most depressing kind — crack mothers, dead bodies, drugs and even some human trafficking — the scenarios seemingly as random in their placement as the gruesome violence that colors them.

The worst of the worst is a Latino gang with ties to Mexico's Sinaloa cartel that keeps surfacing. They are a scary crew with names like Big Evil (Maurice Compte), Wicked (Diamonique), La La (Yahira Garcia) and Demon (Richard Cabral) and a rage that is full-blown crazy. Garcia and Compte are standouts at channeling anger in stomach-churning ways.

Back in the car, the officers pass the time giving each other grief. A pattern soon emerges, because Mike is running this road show: razzing Brian about his new girlfriend Janet (Anna Kendrick), offering up very graphic relationship advice, regaling him with stories of family life with Gabby (Natalie Martinez), who is pregnant with their first child. Kendrick and Martinez do their job to expose the softer side of their guys, but they are really just a few threads woven into the fabric of the partners' lives. There are other good turns around the edges, especially America Ferrera toughening up for her by-the-book cop and David Harbour as bitter, older officer Van Hauser, who the guys relentlessly prank.

But the only relationship that really matters is the one between Brian and Mike. There is a lot of love in that car, and Peña and Gyllenhaal make you feel it. The easy back and forth between them — topics ranging from raunchy nonsense to philosophical musings — have an organic feel that is hard to come by and usually worth the wait. These moments, seeded through the film, nearly always bring tension-releasing laughter, which we need as much as they do.

In Brian, it feels as if Gyllenhaal has finally found his way back home after struggling through a series of roles that didn't quite fit in the years after his "Brokeback Mountain" breakout. He's got a way of playing things so close to the vest that it requires a character with a rich interior life that he can expose in a look or a laugh. As good as Gyllenhaal is in this, Peña nearly steals the show. From the moment Mike Zavala steps into view, he is an LAPD beat cop in every move he makes — whether duking it out with a drunk or dancing with his wife.

Ayer has been best known until now for his searing script for 2001's "Training Day," also a story of cops in L.A. A proven writer, his previous forays into directing — "Harsh Times" and "Street Kings" — have been less skilled, their cop stories more of the same. "End of Watch" is different — distinctive and street worthy.