In the decade since "Training Day," director David Ayer has held a monopoly on realistic, gritty police dramas. His latest effort, "End of Watch," follows two young cops (Jake Gyllenhaal and Michael Peña) who get in over their heads when trying to maintain law and order on the streets of Los Angeles.

MTV News spoke with Peña for our Fall Movie Preview Week, and he filled us in on how he built a real friendship with his onscreen partner and how that relationship made the firefights all the more realistic.

(You can also check out an exclusive clip from "End of Watch" below.)

MTV: What drew you to this project?

Michael Peña: For me, it always starts with the scripts, and this was one of the most interesting cop movies that I've read because it was more about these two dudes — one of them is Latin, one of them is a white guy from the [San Fernando] Valley. I got my roots closer to East L.A. It was about how they interact and how they take care of business. It was about the everyday life of cops and what they really do. I couldn't put down the script because the conversations were really cool, but the action sequences were also really cool. I thought it was something that I had never seen before.

MTV: Where did your conversations with Jake in the patrol car come from?

Michael Peña: I'm going to say that about 98 percent of it is written. We rehearsed and rehearsed and rehearsed. Some scenes were — no lie — rehearsed like 100 times. David Ayer was there. We rehearsed with him a lot, and we talked about all the possibilities. We would improvise some stuff, and he'd be like, "Nah, nah, keep that." It helped improvisation because on the day, if we had an idea, he'd be gone for 20 minutes and come back with three pages of dialogue. He would literally write on the fly. He did that five times during a four-week shoot, so once a week, he'd be like, "Oh, I've got an idea for a scene." The cameras are set up, and he's just like, "Do it."

MTV: What kind of research did you do for the role?

Michael Peña: We went on a bunch of ride-alongs. It got to the point where when you saw some sh-- go down, it wasn't a total surprise. You knew how to handle it. That's when you know you've gone on a bunch of ride-alongs. It just opens your eyes because you think the LAPD is a certain way, but then you see what they have to deal with. It's pretty gnarly. They're trying to help people in certain areas, and they're not liked.

MTV: How did you and Jake build a strong relationship on set?

Michael Peña: David Ayer was really adamant about us spending time together and talking about the characters and what we want to do and plan it out. He has an older sister, and I have an older brother. We just remembered how they'd fight and bicker. I was like, "I remember that totally," and he says, "But you still love the person." In a way, we just kept talking about it and designing how we were with our siblings. We were getting to know each other, but at the same time designing the friendship and the brotherhood. At the end of the day, you have to believe these guys are real partners, and they spend a lot of time together and they have each other's backs. Instead of saying that, showing that is what's really exciting about the script. When you have the action sequences, it really pays off. You're like, "I really don't want these guys to get hurt. I don't want one of them to get hurt."

MTV: Did that relationship make shooting action scenes more intense?

Michael Peña: It [was], in a way, because we put in a lot of work. Every time I was rehearsing a scene that was a shootout or whatever, I wanted to make sure that my partner went home safe and alive. Secondly, I wanted to make sure that my wife and my newborn baby weren't left fatherless. Every time we rehearsed a scene, we would talk about, "Dude, we have to do this for the family." It felt kind of like a sport, where you have these mantras that you keep talking and talking it through so you remember the motivation, why we're playing this thing.

From "Perks" to "Breaking Dawn, " "The Hobbit" to "Skyfall," the MTV Movies team is delving into the hottest upcoming flicks in our 2012 Fall Movie Preview. Check back daily for exclusive clips, photos and interviews with the films' biggest stars.