Bradley Cooper's next big-screen venture sees him take on his most challenging role to date in Clint Eastwood's upcoming biopic, 'American Sniper,' portraying Navy SEAL sniper Chris Kyle, who has more than 150 confirmed kills in his military career.

Bradley Cooper
Cooper portraying Navy SEAL sniper Chris Kyle in 'American Sniper'

Even though portraying a real life war hero is already enough pressure for the Hollywood star, as well as a huge responsibility, the role became even more difficult for Cooper as he only managed to speak with Kyle once before his death.

"We went into the project thinking I would be doing it hand-in-hand with him," he told NPR. "And so I only talked to him one time on the phone, and that was to hope to sort of soften any of the fears he had about what Hollywood would do to his story. And we had a great conversation, but little did I ever think that would be the last time I'd ever get to talk to him, and that I'd never get to meet him. So when he was horribly murdered, everything changed."

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Kyle, 38, was tragically killed by a troubled veteran during an outing to a shooting range in Texas on February 2, 2013.

However, Cooper was very dedicated to playing the SEAL, so he therefore worked closely with Kyle's widow, Taya Kyle, when preparing for the role. 

After creating such a strong bond with the Kyle family, Cooper said he "honestly can't imagine not being in the family's life. But that's up to them. The way I live my life, I'm very good at keeping in touch."

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'American Sniper' hits theatres in the United States on December 25, 2014.