Michael Cuesta did not set out to be a feature film director. In college, he studied photojournalism, he later became a commercial photographer, and eventually worked his way into directing TV commercials. That’s when the filmmaking bug first bit, resulting in directing a series of short films, one of which, titled “Howie,” made it into SXSW. The next step was an attempt at making a feature. Using his own money, along with a some from a few foreign investors, he wrote and directed the art house indie hit “L.I.E.,” a gritty little film about a Long Island teen (a very young Paul Dano) crossing paths with a criminal mentor (Brian Cox). Looking back on it now, Cuesta says, “I had no idea that movie was going to give me a career.”

But first came his career in TV: directing pilots, directing episodes, and producing. Cuesta directed an early installment of “Six Feet Under,” then moved on to do the pilot and some episodes of “Dexter,” and the same for “Homeland” and “Elementary.” His return to directing features happened in 2014 with the journalism-CIA-drug trade thriller “Kill the Messenger.” His newest film, “American Assassin,” marks the first film to be adapted from the popular series of espionage novels by Vince Flynn featuring the unconventional CIA-like agent Mitch Rapp. Cuesta, 54, recently spoke about the film in Los Angeles.

Q: How did you fall into the world of making TV pilots?

A: I made “L.I.E.” right when TV was changing. The timing was perfect. Directors were becoming auteurs in television. Alan Ball, who created “Six Feet Under,” had seen my film at Sundance, fell in love with it, and said, “Let’s get this guy, Cuesta.” So, I was invited to be a director on “Six Feet Under.” I already had a lot of commercial experience, I knew how to run a set, and I used to shoot my own stuff. So, I knew what I was doing. An executive producer on that show, Bob Greenblatt, went on to run Showtime. He and I always talked about doing something on the side, and then he found this book called “Dexter,” so that was my first pilot. That was the pilot that started everything.

Q: What led to you directing “American Assassin?”

A: The script was sent to me a few times when it was in development. But it just wasn’t there yet, and I was doing other things. But about a year and a half ago, after [screenwriter] Stephen Schiff did a pass on it, it came back to me, and I came onboard. They were interested in my take on it, in me really personalizing the story, and having the movie be a little more subjective, and getting into the psychology of Mitch.

Q: You did a lot of reshaping of the script with Stephen Schiff, and then Michael Keaton (who costars as Flynn’s boss Stan Hurley) added some notes of how he wanted to play him. Does that kind of thing happen often?

A: Originally Hurley was a little more cartoonish, like the typical drill instructor. Michael and I first talked about the guy being more psychological, using brains and brawn. His notes came in after that discussion. A lot of it was about stuff that he felt was overwritten. It was like, “What if I don’t say this?” Most actors want to say less dialogue. But it’s not out of laziness. The hardest lines to remember are when the writing is bad or it’s convoluted and not clear. So, Michael was all about shaping that, about making it clearer, not making Hurley such a drill sergeant guy.

Q: The hand to hand fighting is amazing and fresh. Was it a big challenge to make it different from what we’ve seen in other films?

A: We had a great stunt coordinator, Buster Reeves, who is a martial artist. My direction to him was to keep it as scrappy and as dirty as possible, and keep it more in ground fighting. So, MMA (mixed martial arts) is the style, which is do anything you can to win. So that’s what it was and that lends itself to look more realistic.

Q: A lot of people have read a lot of these books, but the movie is different from the book, as it has to be. What message do you have for fans of the book series as far as how to approach the film?

A: I think they’ll love the action, and I think they’ll love how realistic it is. I have to admit that casting Dylan and Michael wasn’t that popular at first. A lot of people said, “What?” But I think we pulled it off and I think people are going to be really pleased.

“American Assassin” opens on September 15.

— Ed Symkus can be reached at esymkus@rcn.com.