Dylan O’Brien is on his way to become a stone-cold killer for the CIA in the first "American Assassin" trailer.

The "Teen Wolf" star plays a young agent in training under the watch of a Cold War veteran, played by Michael Keaton. Based on the preview (above) for the action drama, the training will be as painful as the mission.

The film is based on a New York Times bestseller of the same name, written by Vince Flyyn. It follows O'Brien through the aftermath of his fiancés death, which enrages him enough to risk his life hunting down terrorists.

"American Assassin" opens in theaters on Sept. 15.

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