A Marine allegedly turned his gun on two friends – including Chris Kyle, a celebrated Navy SEAL – at a gun range on Saturday. NBC's Lester Holt reports.

A former Navy SEAL who wrote "American Sniper," a best-selling book about his lethal career as a marksman in Iraq, was shot to death with another man at a gun range near Stephenville, Texas, on Saturday.

Chris Kyle, 38, and the other man were found dead at the shooting range of Rough Creek Lodge on Saturday afternoon, Texas Highway Patrol spokesman Lonny Haschel told KXAS.

The gunman, identified as Eddie Ray Routh of Lancaster, Texas, was arrested after a brief pursuit, Trooper Haschel said. The other victim was named as Chad Littlefield, aged 35.

Routh, 25, was arraigned Saturday night on two counts of capital murder, said Haschel.

Officer Kyle Roberts at the Erath County Jail told the Associated Press that Routh arrived there Sunday morning and was being held on a combined $3 million bond. Roberts did not have information on whether Routh had a lawyer.

Capt. Jason Upshaw of the Erath County Sheriff's Office said Routh used a semi-automatic handgun, which authorities later found at his home, the Associated Press reported.

Routh is in the Marine Corps Individual Ready Reserve, a U.S. military official confirmed. As such, he is not active or drilling with a unit.

Routh's service record shows that he was an armorer with the rank of corporal and served from June 2006 to January 2010. He was deployed three times -- to Iraq, various locations in Europe and the Middle East, and to Haiti.

Kyle, a Texas native who grew up hunting, served four tours in Iraq with Navy SEAL Team 3. His shooting during battles in Ramadi and Fallujah became legendary, and insurgents nicknamed him the "Devil of Ramadi" and put a bounty on his head.

He was credited with 160 confirmed kills, including one in 2008 in which he said he fired from 2,100 yards away -- 1.2 miles.

The Star-Telegram described him as "America's deadliest sniper."

AP/Erath County Sheriff's Office This photo provided by the Erath County Sheriff's Office shows Eddie Ray Routh. He was charged with murder in connection with a shooting at a central Texas gun range that killed former Navy SEAL and "American Sniper" author Chris Kyle and Chad Littlefield, the Texas Department of Public Safety said Sunday Feb. 3.

Haschel said Routh is believed to have shot the victims at around 3:30 p.m. local time (4:30 p.m. ET) before leaving the shooting range and returning to his home in Lancaster in a Ford pickup truck. Erath County Sheriff Tommy Bryant said the truck belonged to Kyle.

Kyle and Littlefield had taken Routh to the range, said Travis Cox, the director of a nonprofit Kyle helped found. Littlefield was Kyle's neighbor and "workout buddy," Cox told The Associated Press on Sunday morning.

"What I know is Chris and a gentleman — great guy, I knew him well, Chad Littlefield — took a veteran out shooting who was struggling with PTSD to try to assist him, try to help him, try to, you know, give him a helping hand, and he turned the gun on both of them, killing them," Cox told the AP.

Kyle's nonprofit, FITCO Cares, provides at-home fitness equipment for emotionally and physically wounded veterans.

Rough Creek Lodge is a resort and conference center about 90 miles southwest of Dallas and 24 miles southeast of Stephenville in the Texas Hill Country. Lancaster is just south of Dallas.

In a February 2012 interview with NBC News, Kyle said he didn’t want to put the number of kills in the book but the publisher insisted.

NBCDFW.com Chris Kyle was credited with 160 kills during his time as a Navy SEAL marksman.

“If I could figure out the number of people I saved, that’s something I would brag about,” he told NBC News' Lester Holt.

After leaving the Navy, Kyle founded Craft International, which provides training to military, police, corporate and civilian clients, Reuters said.

"It just comes as a shock and it's staggering to think that after all Chris has been through, that this is how he meets his end, because there are so many ways he could have been killed" in Iraq, Scott McEwen, who co-wrote "American Sniper," told Reuters.

Kyle appeared on the NBC reality TV show "Stars Earn Stripes" last year.

Kyle was married with two children.

NBC News' Courtney Kube, Jim Miklaszewski and Mark Stevenson contributed to this report.