Editor's note: This report was originally published in the Star-Telegram on April 11, 2012.Last Christmas Eve, as The Star-Spangled Banner filled Cowboys Stadium, Chris Kyle found himself doing a slow burn.He couldn't dial back his rising irritation any more than the mercury in a thermometer could will itself to drop in the heat of the Iraqi desert.When the anthem ended, Kyle extended a tattooed arm and tapped a fellow in front of him."Hey," he said.The spectator turned around."It's polite to take off your hat," Kyle reminded him, "and put it over your heart."The man didn't appreciate being lectured about flag etiquette, but Kyle has strong feelings about citizenship and the treasured symbols of American freedom."If you don't respect the flag, and I see it, I will bring it to your attention," he said, recounting the incident. "And I may not be super polite about it."Kyle, 37, has kept the Stars and Stripes close to his heart, literally. During four combat tours in Iraq, the folded flag was pressed reassuringly against his chest, beneath his body armor.Kyle still has that flag, riddled with bullet holes from the time he brazenly flew it from a building to draw out enemy insurgents.A smaller, tattered Texas flag, framed in glass, hangs on a wall of his North Texas home.On March 20, 2003, Kyle proudly flew it from his desert patrol vehicle as troops from the United States and its allies launched Operation Iraqi Freedom, the invasion that toppled the regime of Saddam Hussein.Kyle served primarily as a sniper and was wounded twice.He provided "overwatch" protection for Marines and other U.S. troops and earned a reputation for his proficiency.According to Army intelligence, he said, Iraqi insurgents nicknamed him al-Shaitan Ramad - "the Devil of Ramadi."That fan at the Cowboys-Eagles game had no idea that the plain-spoken stranger who confronted him is the author of the bestselling memoir American Sniper and a decorated Navy SEAL who claims to be the U.S. military's most lethal sniper ever.More than 150 confirmed killsTo many, Kyle is a patriot, an American hero.War critics consider him a serial killer hired by a criminal government.Kyle will tell you that he doesn't care what others think of his role in battles in and around Baghdad, Fallujah and Ramadi. The 10-year military veteran won't divulge exactly how many enemy combatants he shot, but he says the Pentagon has certified more than 150 of his kills. Some news reports credit him with as many as 255.Kyle's kills exceeded the exploits of legendary Marine Carlos Hathcock, whom Kyle called "the best sniper in the world." Hathcock had 93 confirmed kills in Vietnam.Another Vietnam veteran, Army Sgt. Adelbert Waldron III, held the American record for sniper kills, 109.Kyle, a member of SEAL Team 3, picked off his targets from rooftops or windows of abandoned buildings. Most shots ranged from 200 to 1,200 yards.His longest, most remarkable kill - from 1.2 miles away - took out an insurgent aiming a rocket launcher at an approaching Army convoy.Kyle's first sniper target was a woman.He can still picture her as she opened the door of a small house in a tiny town near Nasiriya.The woman stepped outside, a child near her side.Not far away, 10 Marines were about to begin a foot patrol through the town.Kyle watched from 50 yards away as the woman suddenly produced a yellow object - a grenade - from beneath her clothing.The Marines were approaching.The sniper silently peered through the scope of his bolt-action precision rifle."Take a shot!" Kyle was ordered.He hesitated."She had turned herself into a suicide bomber," Kyle said. "Her intention was to kill herself and blow up the Marines. ... Either way she was going to die."Kyle steadied his breathing, aimed and squeezed the trigger.The grenade dropped.He fired at his target again as the weapon exploded.And so began Kyle's kill count, which steadily mounted as he operated in a "target-rich environment."Rules of engagementEach of his shots was guided by the war's ever-changing rules. Can I shoot, or can't I? he had to ask himself."For the invasion, it was basically a military-age male, meaning 15 and over, whether they had a weapon or not," Kyle said. "Later, the rules changed for insurgents. ... You couldn't just kill someone for carrying a weapon. They had to be demonstrating violence."We need rules of engagement, but they need to be written by commanders on the ground, in that theater, instead of by politicians trying to get re-elected."Aware that he could be charged with murder for shooting without justification, Kyle said he was required to submit a detailed "shooter's statement" after each kill. Date. Time. Location. Distance. What the target was wearing. What he or she was doing.During the second battle of Fallujah, Kyle said, he killed about 40 insurgents. He shot several of them through an apartment window while lying atop an overturned baby crib.From a second-story perch in Ramadi, Kyle spotted two men approaching on a motor scooter. As it slowed down, the rider in back removed a backpack and dropped it into a pothole, setting an improvised explosive device. As the scooter sped up, Kyle fired once from about 200 yards, taking aim at "center mass," the middle of the body."Like a laser," he said admiringly of his .300 Winchester Magnum.With the men still seated upright, the scooter wobbled, veered and crashed into a wall."Bullet went through both of them," Kyle said."The taxpayer got good bang for his buck on that one," he wrote.A clear conscienceKyle drives a big pickup. He enjoys hunting deer, dove, pheasant and turkey. His favorite movie, She Wore A Yellow Ribbon, features John Wayne as cavalry Capt. Nathan Brittles, who is strong, dominant and unapologetic, much like Kyle himself.He graduated from Midlothian High School in 1992 and attended Tarleton State University. He tried to join the Navy in 1996 but was rejected after his physical exam revealed pins in his arm from a rodeo injury.Three years later, Kyle was working on a ranch in Colorado when, to his surprise, a Navy recruiter called and asked whether he still was interested in becoming a SEAL.Repeated deployments strained his marriage to his wife, Taya.Still, Kyle chose to put his country ahead of his young family. He says he loved what he did. He found fulfillment in those war-scarred cities and towns half a world away from home, fighting for and alongside his brothers in arms.Kyle was awarded two Silver Stars, five Bronze Stars with Valor and two Navy and Marine Corps Achievement Medals. He also received the Grateful Nation Award from the Jewish Institute for National Security Affairs."I don't care about the medals," said Kyle, now president of Craft International, a Dallas firm that provides military and law enforcement sniper training as well as private security. "I didn't do it for the money or the awards. I did it because I felt like it was something that needed to be done and it was honorable. I loved the guys."So don't expect him to apologize.He won't.Or feel remorseful.He doesn't.Every person he shot, Kyle said, was trying to harm Americans or Iraqis loyal to the new government. He killed people who wanted to kill him.He sleeps well.As the son of a deacon, as a husband and as a protective father of two young children, Kyle writes, "I can stand before God with a clear conscience about doing my job."