Since retiring from the Navy SEALs, Chris Kyle, whom the Pentagon has deemed as among America's deadliest snipers, would occasionally take fellow veterans shooting as a kind of therapy to salve battlefield scars.
Mr. Kyle, 38, author of the best-selling book "American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History," was with a struggling former soldier on just such an outing on Saturday, hoping that a day at a shooting range would bring some relief, said a friend, Travis Cox.
But the Texas authorities said Sunday that the troubled veteran turned on Mr. Kyle and a second man, Chad Littlefield, shooting and killing both before fleeing in a pickup truck.
"Chad and Chris had taken a veteran out to shoot to try to help him," Mr. Cox said. "And they were killed."
The police identified the gunman as Eddie Ray Routh, 25, who had served in both Iraq and Afghanistan and had suffered from mental illness. The police offered no information about a possible motive.
Mr. Routh shot the men about 3:30 p.m. on Saturday at the Rough Creek Lodge, an exclusive shooting range near Glen Rose, Tex., about 50 miles southwest of Fort Worth, Sgt. Lonny Haschel, a spokesman for the State Department of Public Safety's Highway Patrol Division, said in a statement. Mr. Routh was arrested on Saturday night at his home in Lancaster, a suburb south of Dallas. He has been charged with two counts of capital murder, Mr. Haschel said.
Mr. Cox, the director of a foundation that Mr. Kyle created, said he did not know Mr. Routh. Mr. Kyle, he said, had devoted his life since his retirement from the military to helping fellow soldiers overcome post-traumatic stress.
In 2011, Mr. Kyle created the FITCO Cares Foundation to provide veterans with exercise equipment and counseling. He believed that exercise and the camaraderie of fellow veterans could help former soldiers ease into civilian life. "He served this country with extreme honor, but came home and was a servant leader in helping his brothers and sisters dealing with post-traumatic stress disorder," Mr. Cox, also a former military sniper, said by telephone.
Mr. Kyle, who lived outside of Dallas, had his own difficulties adjusting after retiring from the SEALs in 2009. He was deployed in Iraq during the worst years of the insurgency, perched in or on top of bombed-out apartment buildings with his .300 Winchester Magnum.
His job was to provide "overwatch," preventing enemy fighters from ambushing Marines as they moved through Iraqi towns.
He did not think the job would be difficult, he wrote in his book, but two weeks into the war, he found himself staring through his scope into the face of an unconventional enemy. A woman with a child had pulled a grenade from beneath her clothes as several Marines approached. He hesitated, he wrote, but then fired the shot.
"It was my duty to shoot, and I don't regret it," he wrote. "My shots saved several Americans, whose lives were clearly worth more than that woman's twisted soul."
Over time, his hesitation diminished and he became better at his job. He was credited with more than 150 deaths. He became the scourge of Iraqi insurgents, who put a price on his head and were said to have called him the "Devil of Ramadi." In his book, he describes taking out a fighter wielding a rocket launcher 2,100 yards away, a very long distance for a sniper and the longest for Mr. Kyle.
"Maybe the way I jerked the trigger to the right adjusted for the wind," he wrote. "Maybe gravity shifted and put that bullet right where it had to be."
"Whatever, I watched through my scope as the shot hit the Iraqi, who tumbled over the wall to the ground."
Mr. Kyle received two Silver Stars and five Bronze Stars for valor.
He would later describe his service in humble terms, preferring to talk not about the enemies killed, but the lives saved.
"I feel pretty good because I am not just killing someone, I am also saving people," he said in a January 2012 interview with The Dallas Morning News. "What keeps me up at night is not the people that I have killed, it is the people I wasn't able to save."
In an interview with The New York Times in March, Mr. Kyle said that he had hesitated to write a book about his experiences. But he was persuaded to do so after hearing that other books about SEALs were in the works.
"I wanted to tell my story as a SEAL," he said. "This is about all the hardships that everybody has to go through to get the respect and the honor."
But he also wanted his sense of humor to come out, he said, noting that he tried to "write in a Texas drawl."
The book, which was published in January of last year, spent months on The New York Times best-seller list and turned Mr. Kyle into a celebrity. He appeared on talk shows like "Conan" with Conan O'Brien.
He also played a role in the NBC reality program "Stars Earn Stripes," in which celebrities were paired with elite soldiers to carry out military-style missions.
For all his success, friends and fellow veterans described Mr. Kyle as a humble warrior and down-to-earth family man who loved his wife and two children. In gatherings with other veterans, he would deflect the praise of well-wishers and play up the achievements of his comrades.
"He wasn't the 'American Sniper' to all of his friends," Mr. Cox said. "He was Chris Kyle, and he was right alongside you. He was proud to be a veteran, and he would do anything he could to serve veterans."
Manny Fernandez and Julie Bosman contributed reporting.
This article originally appeared in The New York Times.