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Bradley Cooper and Sienna Miller portray the real-life couple Chris and Taya Kyle in Clint Eastwood’s “American Sniper.” Chris is a Navy SEAL deployed in Iraq, and Taya is his wife, tasked with taking care of the family back home in Texas.

Cooper told FOX411 that Chris Kyle was “such an interesting charismatic figure as a man,” and how awful it was when he was murdered by another former soldier before they made the film.

“It just became quite a responsibility to tell the story,” Cooper said. “We felt like we wanted to tell it, and Taya said you know, if you’re going to do it, do it right, get it right, and let’s tell it now.”

The film’s positive reception by the Academy Awards – six nominations including Best Picture and Best Actor for Cooper -- was a big surprise. But the most rewarding reactions to the film, Cooper says, have been from veterans.

“It's been incredible, just incredible the amount of response. It’s everything we could have possibly hoped for,” he said. “In the sense of people feeling like even though it's a movie it's accurate enough, and in terms of the emotional and sort of familial sort of sense of reality that it's completely accurate."

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    Miller said having Taya on board was key.

    “She had tons of home videos and we read all of their email correspondence when he was on tour.  She kept everything because she never knew whether he'd make it back,” Miller told FOX411. “You know, when you have access to that kind of information you get a side to someone that no one really ever sees. You see the family man, you see how loving he was, and I think that Bradley really brings that heart, that balance between him as the military man but also this soulful, loving father."

    Cooper said playing Kyle provided insight into the lives of soldiers and their families.

    “It was a keyhole into that life,” he said. “One thing that we were able to do was explore this man's life and this woman's life and their children and their family and in doing so hopefully get just a nugget, a kernel of truth, that people who actually have gone through it and are going through it can relate to it and not feel alone.”

    “American Sniper” opens in theaters nationwide January 16th.