It is loosely based on the memoir American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History (2012) by Chris Kyle, with Scott McEwen and Jim DeFelice.
Den er baseret på bogen American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History af Chris Kyle med Scott McEwen og Jim DeFelice.