An upcoming movie starring Bradley Cooper honors the most lethal sniper in U.S. history.

“American Sniper” is about Navy SEAL Chris Kyle, who served four tours in Iraq and had 160 confirmed kills. His primary objective was to protect his fellow warriors.

For the role, Cooper gained 40 pounds of bulk, trained with Navy SEALs and even spoke with Kyle, promising to stay true to his story.

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Bradley Cooper to Star as Chris Kyle in 'American Sniper' Movie

Shortly after that conversation, Kyle was fatally shot at a Texas gun range. An ex-Marine, who Kyle was trying to help through PTSD, is accused in the murder.

Clint Eastwood directed the movie, which comes out on Christmas Day.

Check out the trailer below.