O'Brien knows what it's like to come out of the other side of a traumatic incident, and he used it to bring this character, based on the one created by Vince Flynn for a series of novels, from page to big screen.
"I felt like I really understood this character in a way more than I ever could have, funny enough," he told CNN.
In March 2016, O'Brien was seriously injured while filming the third film in the "Maze Runner" franchise.
The actor suffered multiple injuries, including a facial fracture, and production on the film was shuttered for months.