If there’s a formula for directing authentic cop dramas, director David Ayer has figured out the technique.

Ayer, who scripted “Training Day,”  “SWAT,” “Dark Blue” and directed “Harsh Times,” had planned to hang up his LAPD jersey after directing the gritty cop drama “Street Kings” in 2008, but something prompted him to make another cop flick.

“A friend of mine who is a cop and his colleagues all bring video cameras to work with them and he had shown me this footage, which was incredible.  It was cops filming themselves, which I have never seen before, and I thought that would be a fantastic technique to tell the story that way.”

For the director who grew up on the streets of South Central Los Angeles, life could have turned out very differently. He saw his neighborhood ripped apart by gang violence, has been arrested a few times, and severely beaten by law enforcement as a teenager, but instead of contributing to it, Ayer began channeling those experiences into stories while serving in the U.S. Navy.

“It was pretty clear that I was headed down a certain road here,” he says. “But one of my mentors (acclaimed screenwriter Wesley Strick) in the business told me to find my niche and exploit it. So that’s when I said, I know this—I’ve got to get back to this.”

His latest movie “End of Watch” is a grim, brutal cop drama that is impossible to ignore. While his previous works centered on gangster cops or corrupt cops, this movie offers a first-hand experience of the day to day life of two Los Angeles Police Department officers.

“The thing about the cop genre is that we haven’t seen what they really do at work,” Ayer explains. “We’ve seen what Hollywood thinks they do. LAPD has had a bad rap over the years, and what I learned is that most of these officers do care and that is the side I wanted to share. These guys see mayhem and carnage, and are faced with incredible psychologically destructive situations, and then they have to go home and put work into a relationship. Somebody who can do that successfully to me is a fascinating person.”

The movie tells the story of two best friends (Jake Gyllenhaal, Michael Peña) and what they go through on the police force, and although it is riddled with action and violence, it’s ultimately a story about friendship and family — universal themes Ayer hopes will resonate with everyone.

“I wanted to capture the story of guys that go out there, work hard, do their job, and are fundamentally good people,” Ayer says. “What we’ve been trained to expect from a cop film is not going to be met in this movie. It’s the reality of it. It’s the boredom of it. It’s how people connect, how cops connect to each other. This is really about being let into a secret world.”

There’s a lot to appreciate in “End of Watch.” Ayer piles on one incident after another starting off with a heart-pumping car chase as Officer Brian Taylor (Jake Gyllenhaal) and Officer Mike Zavala (Michael Peña) are racing through the backstreets of the Newton jurisdiction of South Central Los Angeles attempting to catch a car full of gang-bangers, while a dash cam car captures the chase. It ends in a barrage of bullets— one catches Taylor’s Kevlar vest— just another hazard of the job. The picture may feel more than a little familiar, but Ayer knows how to cook up intense scenes. With each new dispatch comes uncertainty for the two young officers and the things they discover will jolt you out of your seat physically and emotionally.

 “End of Watch” is a murky cop thriller which unfolds like a documentary. The action is aggressive and bloody and the language is incessant, with the favorite term being the standard cop-movie expletive, “f–k.” but Ayer knows what he’s doing, after all, it is familiar territory.

“To go from ‘Training Day’ to ‘End of Watch’ is in a lot of ways, to complete a circle,” says Ayer. “Something about writing cops is easy for me. I have the ‘I-can-write-about-cops’ gene.”