With his squinty eyes, baby face, and big build, Kevin Lacz sort of resembles tough guy actor Tom Hardy. Perhaps it’s why director Clint Eastwood and star Bradley Cooper felt Lacz should play himself, a fellow Navy SEAL in Chris Kyle’s unit, in the Hollywood blockbuster American Sniper. The film has, of course, become a bona fide phenomenon, grossing close to $300 million stateside and receiving 6 Oscar nominations, including Best Picture.

But Kevin Lacz is no actor. He enlisted in the Navy SEALs in 2002, following the death of his friend’s father during 9/11, and served two tours in Iraq in 2006 and 2008. There, he did two platoons at SEAL Team 3 (Charlie and Delta) where he worked as a sniper alongside Chris Kyle, who became a mentor and good pal.

His involvement in American Sniper dates back to 2010 when Kyle rang him up asking if Jim DeFelice could interview him for his book of the same name. He obliged. Two years later, the film adaptation of the book was being set up and Lacz’s wife reached out to Jason Hall, the film’s screenwriter, over Facebook to tell him to “do the story justice.” He replied, “Well, help me do it then.” She put him in touch with Lacz, who advised him on technical matters for the script—guns, the art of being a sniper, direct action missions. Hall finished the script and one day later, Kyle was murdered. Lacz invited Hall down to Kyle’s memorial service in Texas, and served as a liaison between him and Kyle’s fellow SEALs.

Sniper producers Rob Lorenz and Andrew Lazar eventually hired Lacz as a technical adviser on the film, and he met up with Bradley Cooper at the shooting range in February 2014. About two hours into the shoot, Cooper looked up from his gun and said to him, “Hey, did you ever think about playing yourself in the movie?” Lacz was speechless.

Cooper convinced Eastwood to let him audition, and he tried out for the role of a contractor who gets shot on the side of the road, and playing himself—or “Dauber,” his SEAL nickname. Lacz shot an audition tape in his wife’s great aunt’s kitchen in Vermont, and sent it over to Eastwood. The grizzled filmmaker came back with a message he’ll never forget: “The boy’s damn good! Get him the job.”

THE DAILY BEAST: Do you remember the first time you met Chris Kyle? KEVIN LACZ: I had gotten to SEAL Team 3 and the guys hadn’t come back yet. You started to hear guys were doing good things overseas, and there was a guy who’d had 20 some-odd kills in Fallujah, and it was Chris. It started painting the picture of a guy who was setting himself apart. He was called “Tex” back then, but then people started joking around and calling him “The Legend” because he was pretty legendary in Ramadi.

But the first time I met Chris, I just walked into the platoon space and that’s how I got my nickname “Dauber.” My LPO was there and Chris was there, and I had ambled in—and had more blond hair back then—and they just said, “Dauber.” I was like, “What the fuck does that mean?” I guess it was from Coach. It could’ve been worse. Chris was older, too, so we’d joke around and call him “Old Balls” every now and again, and then he’d choke you out and shit. But with Chris, as a new sniper in the platoon, you study the people you work with because you want to be at that level, and Chris was someone I studied, and who was a mentor to me.

What about him made him become the “deadliest sniper in U.S. history?”

The dedication. He had this uncanny ability to just sit on that scope and have this situational awareness of what’s going on. In the movie they show deliberate guys planting IEDs, but in real life, it’s a little bit more inconspicuous. You have to be watching at all times because it can just be a quick flash. Chris was just focused. He’d be the first one to tell you he wasn’t the best shot in the world, but he had more dedication.

He’d say he wasn’t the best shot?

He’d be the first to tell you. He’d take a lay-up over a 3-pointer any day. He was a center mass shooter, which is what made him very effective.

Your first deployment to Iraq came in 2006. And that was a very tough deployment—the Battle of Ramadi.

The "Sunni Awakening" was occurring in western Iraq and Ramadi was an experiment. How are we going to tackle this? We used the tribal engagement model—winning the hearts and minds and establishing confidence with the locals and village elders, and having that permeate the town. It was a gnarly deployment. Chris had 101 kills, and we had 200 some-odd kills as a unit.

All the times Chris got shot aren’t in the movie, but what were some of the closest calls your unit had?

One time we were on the rooftop of an apartment complex, and they do a lot of fire-and-move. We’d been engaging a lot of targets throughout the day, and all of a sudden came under a bunch of machine gun fire. They’d taken a big ol’ 155mm round and put it at the door where they thought we were going to come out. As we were getting ready to leave and had a bunch of people by that door, our Explosive Ordinance Disposal guy saw the round and called everybody back from the door. And there was a wire going from the round across the street to where the guys were waiting to blow everyone up. That was the closest call.

Also, Chris took one off the helmet in Baghdad. It just ricocheted off the helmet. He also took one off the plates. Another time, I was in a hide site with Chris and my buddy Jason stood up and took a round right off his night vision. There was this big flash of light.

A big subplot of the movie is the cat and mouse game between Chris Kyle and the Syrian sniper on his tail. How realistic was that? Was there actually a sniper on his tail?

I think the Mustafa character was really a metaphor for all insurgent marksmen. The threat was very real, and when you’re patrolling through the streets you all look the same, but when you’re set up in a house for 24 hours they know that there’s probably a sniper element there. The Butcher also shows the brutality of the insurgency. He’s a small character, but he’s powerful.

Right. That scene where he takes a drill to the boy’s head is horrifying. Were there insurgents over there who you witnessed commit comparable acts of brutality?

Sure. We went after a lot of IED makers, but also terror squads—like what we’re seeing right now with ISIS. Also, we went after Zarqawi and those guys who instilled a lot of fear among the locals. It’s not like ISIS now because we were hunting them down at the time.

Had you spoken with Chris when he returned about suffering from any sort of PTSD? There is that very good scene in the bar when he returns from his fourth deployment and is on the phone with his wife, and he breaks down.

I didn’t speak with him about that. But it’s a night-and-day difference going from shooting people to taking your family out to dinner. It affects everyone differently. You really need to know how to dial it up and then dial it down. PTSD isn’t even overtly mentioned in the movie, but the film opens the discussion about it. And I think that’s great because it’s a very real issue that a lot of veterans struggle with—and not just veterans, but police and first responders, too.

How’s Bradley with the rifle?

He’s a natural. I’m not just saying that. By the end of the second day, he was hitting head plate targets at 600 meters with a .338 Lapua. I didn’t know what baseline he had, so he just said, “Teach me everything.” We started with basic SEAL marksmanship, shooting, moving, and communicating, close quarters combat, and just the SEAL mindset.

Michael Moore made some controversial statements about how he didn’t believe that snipers like Chris Kyle were courageous, or heroes. That must have rubbed you the wrong way as a sniper.

You know, I don’t think the film glorifies Chris’ actions as a sniper. It’s a character study that dramatizes his journey. I’ve gotten a lot of response back from the movie, and it’s all been positive. The biggest validation is when a veteran or active duty soldier comes up to you and complements it. Men and women in the military know what’s really going to hurt them, and it’s not comments. It’s RPGs and bullets.

How do you and other Navy SEALs feel about Jesse Ventura successfully suing Kyle for slander for making up a story in his book, and then collecting $1.8 million from his widow?

I think what outshines that is the good that Chris has done, and how much he did to help veterans. It’s tough to see that, but we support Chris, and we support the team.

Because of the success of the film, critics have been dissecting Chris’ book and have been very critical of how he refers to insurgents as “savages” throughout the text. What are your thoughts on that?

You know, there’s always going to be criticism. People hate talent and they always try to take down the best. People are always hating on Tiger Woods and Kobe, too. Chris was always very stoic when it came to that stuff, and didn’t really give it too much of his time.

How much did Chris buy into his own title of “The Legend?” In addition to Ventura, there are of course the tall tales he’s told about picking looters off from the top of the Superdome during Hurricane Katrina and shooting down a couple of carjackers. How do you reconcile those tall tales with the man that you knew?

You know, I challenge people to try and find out who the real Chris Kyle was themselves. Talk to his mom, talk to his wife, and talk to his friends. Don’t just listen to the critics.