His first kill was a woman who cradled a toddler with one hand and held a grenade in the other.
"I had to do it to protect the Marines," Kyle told Time magazine a year ago. "You want to lose your own guys, or would you rather take one of them out?"
Standing 6 feet, 2 inches tall and weighing a muscular 220 pounds, Kyle developed a deadly reputation in Iraq, prompting insurgents to put a bounty on his head, according to his autobiography.
"I'm a better husband and father than I was a killer," he told Time. "I'm pretty comfortable with not having to kill anyone. Now, don't take deer hunting away from me."
When Kyle's military career ended after a decade, he joined other former SEALs to start Craft International, a security company with the motto "Despite what your momma told you, Violence does solve problems."
He also became a best-selling author, a reality TV personality, a supporter of fellow vets suffering from post-traumatic stress syndrome, an avid hunter and an outspoken opponent of gun control.
Kyle, 38, was shot to death Saturday
-- by a former Marine, police say -- while shooting for fun on a Texas gun range. Another man was also fatally shot.
A west Texas native, Kyle studied agriculture at Tarleton State University in Stephenville, Texas, after graduating from high school in 1992. He left college after two years to work as a ranch hand until he joined the Navy in 1999.
He left the Navy as a chief petty officer in 2009 with a chest full of medals, including two Silver Stars and five Bronze Stars, according to his service record released by the Pentagon.
It was another distinction accumulated during Kyle's five tours of Iraq that has brought him the most attention. He wrote about it in a best-selling book published a year ago, titled "American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History."
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."
Kyle acknowledged in his deposition saying that he hated Ventura "with a passion."
His relationship with another politician was warmer. His company did some security work for former Alaska Gov. Sarah Palin, whom he met while on the "Stars Earn Stripes" reality TV show with her husband, Todd.
"Chris was a wonderful man, a good friend, and a true American hero who loved our country and served honorably. He was loved and admired by so many, and he will never be forgotten," the Palins said in a statement Sunday.
Much of Kyle's time since leaving the military was spent building Craft International, which offers military training for law enforcement and provides security services.
His company also organizes "civilian and corporate shoots" at gun ranges, he said. "It is only fun day shoots, self-defense, or weapons familiarization," he said.
In a Guns.com interview at a gun dealers convention in Las Vegas last month, Kyle was asked about President Barack Obama's gun control proposals, which he said he believed to be aimed at "trying to ban everything."
Banning 30-round magazines for assault rifles would be "opening the door to start taking more of our rights," he said.
Correction: Earlier versions of this report incorrectly described the military background of Chad Littlefield, who was killed with Chris Kyle. Littlefield was not a veteran.