TORONTO—David Ayer calls it “a run and gun”. In a hotel room to discuss his gritty (but humour-laced) cop drama End of Watch, which was screening at the Toronto International Film Festival, the writer-director told the Georgia Straight that the film’s five-month rehearsal and three-week shooting process amounted to a kind of “controlled chaos”. He added that the cast and crew—in particular, stars Jake Gyllenhaal and Michael Peña—become almost psychic. “We all knew what everybody was thinking,” he said.

Ayer, who comes from a military background, admitted that there’s no other venture that parallels the military quite like a movie set, particularly in terms of discipline. Yet the script took him just six days to write. “Boy, I wish they were all so easy,” he quipped before adding that End of Watch, which opens in Vancouver on Friday (September 21), was really simmering away for more like six days and 20 years. “It’s actually very complex and very technical, and the story wiring is kind of buried beneath this veneer of fake reality,” he said.

The inspiration for the script, he revealed, came from a friend who suggested doing a “found footage” cop movie. Ayer was shown some videos, which he found riveting. “I thought, ‘This is a fantastic tool to tell this story,’ ” he said. “As a filmmaker, you can’t beat reality. I think that the best stories always come from the truth.”

Ayer also saw the opportunity to shift the focus from the “corrupt cop thing that everyone’s been beating to death for the past 10-plus years”—including his own films (he wrote 2001’s Training Day and directed Street Kings in 2008). Instead, End of Watch wants to show us the heart in the men and women behind the badge. “They are going into harm’s way on our behalf daily,” Ayer stated. “There’s something really honourable about that.”

At its core, the film is about friendship and putting it on the line—“It’s about two best friends just trying to figure out how to live their lives,” the director said—and the movie hinges largely on the chemistry between Gyllenhaal and Peña. Yet Ayer had no idea if they were going to work well together. It was a real gamble, he admitted.

“At first, they were very professional with each other, and very serious, and I was like, ‘Huh, this movie is about best friends and I don’t know how you get these guys there,’ ” he said. The rehearsal process took care of that. The intense shared experience of tactical training—which involved shooting real guns, sparring, going on cop ride-alongs, and pulling gangsters out of cars in South L.A. at 3 a.m.—Ayer noted, worked together to bond his actors and turn them into true friends.

“This is probably the most I’ve been involved in a character,” Peña said, joining the director. Peña added that his role called for real openness and vulnerability along with all the physical challenges. “It was pretty gnarly,” he remarked. “We went through good times and bad times, and that’s what makes this movie truly special: that there is that thing where you’re actually seeing interesting conversations and you’re in the car with these guys. They don’t know that the camera is on, or they forget, or they get used to it, but whatever it is, you’re living this ride with these guys.”

Watch the trailer for End of Watch.