Chris Kyle, a retired Navy SEAL and the U.S. military's most lethal sniper, was fatally shot Saturday along with another man on the gun range of Rough Creek Lodge, a posh resort just west of Glen Rose, Texas, Erath County Texas Sheriff Tommy Bryant said.

A suspect was arrested about five hours later in Lancaster, southeast of Dallas, more than 70 miles from the scene, Bryant said.

The suspect, identified as Eddie Ray Routh, 25, was pursued to a house in Lancaster by officers, including a local SWAT team. Routh tried to flee in a vehicle but was stopped about 9 p.m. after spikes were laid across a road, Bryant said.

"The suspect has been caught and is in custody in Lancaster," he said. Erath County sheriff's investigators and Texas Rangers were securing a capital murder warrant, he said.

Witnesses told sheriff's investigators that the gunman opened fire on the two men around 3:30 p.m., then fled in a pickup belonging to one of the victims. The Sheriff's Department didn't get a call until around 6 p.m.

Rough Creek Lodge is 77 miles southwest of Fort Worth between Glen Rose and Hico.

The motive for the shootings remains unclear, Bryant said. "Not a clue, absolutely no idea."

WFAA/Channel 8 quoted unnamed sources as saying that Kyle, who lived in Midlothian, and a neighbor had taken Routh on an outing to help him deal with post-traumatic stress disorder. Routh turned on the men and shot them in the back, the report said.

The sheriff said he could not confirm how the victims were shot.

In January 2012, the Cleburne Times-Review reported that Routh, of Lancaster, was arrested in Johnson County on suspicion of driving while intoxicated. Public records show that Routh previously lived in Camp LeJeune, N.C., a major Marine base.

Kyle, 38, who is survived by a wife and two children, was the author of American Sniper, a 2012 autobiography.

A 1992 graduate of Midlothian High School, he attended Tarleton State University. He tried to join the Navy in 1996 but was rejected after a physical exam revealed pins in his arm from a rodeo injury.

Three years later, Kyle was working on a ranch in Colorado when a Navy recruiter called. He was trained as a sniper and served 10 years.

He never disclosed exactly how many enemy combatants he shot, but the Pentagon certified more than 150 of his kills during four tours in Iraq. Some news reports credited him with up to 255. His confirmed 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.

In all, Kyle was awarded two Silver Stars, five Bronze Stars with Valor, and two Navy and Marine Corps Achievement Medals.

"I don't care about the medals," Kyle told the Star-Telegram in a 2012 interview. "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."

A member of SEAL Team 3, Kyle picked off his targets from rooftops or windows of abandoned buildings during the 2003 invasion of Iraq, which toppled Saddam Hussein. Primarily serving as a sniper and wounded twice, he provided "overwatch" protection for Marines and other U.S. troops and earned a reputation for his proficiency.

Most shots ranged from 200 to 1,200 yards. His longest and most remarkable kill -- from 1.2 miles away -- took out an insurgent aiming a rocket launcher at an approaching Army convoy.

During the second battle of Fallujah, Kyle said, he killed about 40 insurgents. He shot several 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, the rider in back dropped a backpack 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 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.

According to Army intelligence, he said, Iraqi insurgents nicknamed him al-Shaitan Ramad -- "the Devil of Ramadi."

After the service, Kyle became president of Craft International, a Dallas firm that provided military and law enforcement sniper training as well as private security.

The deadliest sniper in U.S. military history was scheduled to speak Feb. 27 at Tarrant County College Northwest Campus in Fort Worth. The four-hour presentation, "Preparing a Warrior's Heart," was to cover having the "mindset" for survival, being prepared for a fight and "being OK in the aftermath."

Kyle wrote in American Sniper that he had zero remorse for his combat kills. Every person he shot, he said, was trying to harm Americans or Iraqis loyal to the new government.

As the son of a deacon, as a husband and as a protective father of two young children, Kyle wrote, "I can stand before God with a clear conscience about doing my job."

Staff writer Susan McFarland contributed to this report, which includes material from the Star-Telegram archives.