Not only does he go shirtless in the beginning, but he bulks up throughout the film and looks totally jacked by the end. Check out stills from the trailer in the gallery below!
The film follows the rise of Mitch Rapp (O’Brien), a CIA black ops recruit under the instruction of Cold War veteran Stan Hurley (Michael Keaton).
The pair is then enlisted by CIA Deputy Director Irene Kennedy (Sanaa Lathan) to investigate a wave of apparently random attacks on both military and civilian targets.
Together the three discover a pattern in the violence leading them to a joint mission with a lethal Turkish agent (Shiva Negar) to stop a mysterious operative (Taylor Kitsch) intent on starting a World War in the Middle East.
American Assassin hits theaters on September 15.