Actors Dylan O'Brien and Taylor Kitsch talk new movie "American Assassin"

The world met fictional CIA super-agent Mitch Rapp back in 1999 in a series of novels by the late author Vince Flynn. Now, the character is moving to the big screen in "American Assassin."

Stars of the action thriller, Dylan O'Brien and Taylor Kitsch, joined "CBS This Morning" to discuss the new film, working with Michael Keaton and doing their own stunts.

O'Brien portrays Mitch Rapp, a "black ops" recruit who is working under the supervision of a Cold War veteran played by Michael Keaton, while Kitsch plays a more mysterious operative who seems to be intent on starting a war.

"For me it was a big reason to sign on," Kitsch said of working with Keaton. "I have one long scene with him that's a pretty rare, memorable scene. You know he's just a gamer, still has great energy, improv was big."

The two did the majority of their own stunts on the CBS Films and Lionsgate joint production. O'Brien was hospitalized last year after a vehicular stunt went awry during the filming of "Maze Runner: The Death Cure." The actor suffered multiple broken bones and production had to be halted.

"You have to go about it in a meticulous way. I think it's just easy on set to kinda get lost in that kind of world of make believe and you have to remember that things are still real. Everyone has to do their part," O'Brien said. 

Kitsch said they hoped to "ground" the story in the characters' relationships with one another and not "over-dramatize" the story.

"It's not going anywhere — this terrorism, everything that's going on and these events. So I think that's a really big part of this movie," Kitsch said.

Vince Flynn's widow visited the set during the filming.

"It's a really heartwarming thing. I think it's an honor for all of us to be able to finally bring this to life," O'Brien said.