Chris Kyle was the most lethal sniper in U.S. military history, serving four tours in Iraq with 160 confirmed kills, before being tragically killed by a veteran he was trying to help.

The much-anticipated film about Kyle's life, "American Sniper," is set to hit the big screen on Christmas Day.

Gretchen Carlson sat down with his widow, Taya Kyle, for an exclusive interview to discuss how the film came to life.

Taya said that the filmmakers spent a lot of time absorbing the details about her husband and making sure they got them right on screen.

She added that Bradley Cooper and Sienna Miller, who play Chris and Taya in the film, and director Clint Eastwood all put so much heart and effort into the movie.

"The biggest compliment to them is that people who were close to Chris and people who are close to me have watched it and forgot that they were actors playing a role and have been absorbed," Taya said.

She said the movie captures that Chris was a reluctant hero and would never seek the spotlight.

"Even doing a book in the first place was a really uncomfortable thing for him and something he resisted for a long time," Taya explained.

She said that her relationship with Chris was one of deep, passionate, real love.

"I'll never have anything like that again," she said. "And I'm OK with that, because it was special and it deserves to be set in a separate category."

"He changed me into somebody much, much better, and I'm grateful to him. So I just carry him with me. I feel him with me all the time and that's a pretty special thing, too."

Watch more above and see the "American Sniper" trailer below.