Although the military does not release such statistics, the book claimed Kyle had 160 confirmed combat kills from a distance of up to 2,100 yards. He holds the record for a U.S. military sniper, previously set at 93 by Marine sniper Carlos Hathcock during the Vietnam war.
Kyle seemed humble during a guest appearance to promote his book on TBS' "Conan" last year.
"I had more kills, but that doesn't mean I'm better than (Hathcock) is," Kyle said. "I was just put into a position where I had more opportunities. I definitely cheated. I used a ballistic computer that tells me everything to do. So, I was just a monkey on a gun."
He showed O'Brien a sense of humor when talking about the $80,000 bounty placed on his head by Iraqi insurgents. "I was worried about my wife coming home, because I thought my wife would turn me in," he joked.
Kyle modestly acknowledged to the Time interviewer that he was "decent" at killing.
"The first time killing someone, you're not even sure you can do it," he said. "You think you can, but you never know until you actually are put in that position and you do it. ... And then, you're worried when you get home, are the politicians going to hang you out to dry and put you on trial for murder?"
Did he regret any of his 160 kills? "No, not at all," he told Time.
Kyle's opinion of the American public's ability to understand war was poor.
"For the most part, the public is very soft, you live in a dream world," he said. "You have no idea what goes on the other side of the world, the harsh realities of what these people are doing to themselves and then to our guys. There are certain things that need to be done to take care of them."
His combat persona, though, could be turned on and off, he said. "You're a little more aggressive when you're at work and when you come home, you relax and try to be the different person," he said.
Kyle helped established the FITCO Cares foundation, a charity that helps U.S. war vets "who have survived combat but are still fighting to survive post-traumatic stress disorder," the group's website said.
Life back home was a challenge for Kyle, who acknowledged that he turned to alcohol for comfort at one point. "After I was discharged from the military, it was difficult trying to become a civilian," he told a lawyer during a deposition for a lawsuit last November.
"You're in a combat zone one day," he said. "You come home, and then you have to readjust, and it takes a few days. We just sit in the house, hang with the family and then things get better. But it's simple things of trash blowing across the road, reminded of an (improvised explosive device), you might want to swerve. So that's why you just stay at home."
Former Minnesota Gov. Jesse Ventura filed a lawsuit last year accusing Kyle of defaming him in the book by exaggerating his description of a fight between the two at the wake for SEAL Mikey Monsoor, who was killed in Iraq in 2006.
The book quoted Ventura, also a Navy veteran, as saying he "hates America" and telling Kyle, who was mourning the death of a SEAL teammate, "You deserve to lose a few." Kyle described punching Ventura out at the Coronado, California, bar.
In the suit, Ventura denied making the statements in the book, contending that "the entire story about a confrontation with and physical assault and battery of Governor Ventura was false and defamatory."
At his deposition last November, Kyle continued to insist his book accurately described his clash with Ventura.
"He was complaining about the war, that we shouldn't be there," Kyle testified. "Complaining about Bush, that, you know, Bush was a war criminal. How we were killing innocent men and women and children overseas."
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