A former Marine and Iraq War veteran was arraigned early Sunday in connection with the shooting of former Navy SEAL and “American Sniper” author Chris Kyle and his friend.

According to the Erath County Sheriff’s Office, Eddie Ray Routh, 25, has been charged with two counts of capital murder for the fatal shooting of Kyle, 38, and Chad Littlefield, 35.

Suspect Eddie Ray Routh shown in a mug shot Sunday. (Erath County Sheriff's Department)

Erath County Sheriff Tommy Bryant told CNN the three men had apparently gone to the shooting range together.

The Associated Press reported the two men were shot with a semi-automatic handgun at a shooting range in Erath County, Texas, located about 50 miles southwest of Fort Worth. The bodies were found approximately two hours later.

Texas Department of Public Safety spokesman Lonny Haschel told The Dallas Morning News that Routh tried to flee from the police, but was arrested near his home in Lancaster, Texas. The Dallas Morning News also reported that Routh is being held at the Erath County jail on a $3 million bond.

No motive has been identified in the shooting, but police believe Routh suffers from post-traumatic stress disorder relating to his military background, according to the Associated Press.

READ MORE: Suspected Navy Seal Murderer Had PTSD

Capt. Jason Upshaw of the Erath County Sheriff’s Office said it is unclear if Routh was on any medication at the time of the shooting.

“I don’t know that we’ll ever know. He’s the only one that knows that,” Upshaw told the AP, regarding the shooter’s motive.

The U.S. military confirmed Sunday that Routh served as a corporal in the Marines from June 2006 to January 2010. He was deployed to Iraq in 2007 and Haiti in 2010. His current duty status is listed as reserve.

Kyle is best known as the author of the best-selling book, "American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History," which details his 150-plus kills of insurgents from 1999 to 2009. In the book, Kyle said a bounty had been put on his head by Iraqi insurgents as a result of his significant role in the war. According to promotional information from book publisher William Morrow, Kyle deployed to Iraq four times.

Since retiring from the military, Kyle had been actively helping other military veterans recover from PTSD, according to Dallas-Fort Worth TV station WFAA.

Kyle helped found the FITCO Cares Foundation to help his fellow veterans.

Travis Cox, director of the foundation, told the Associated Press on Sunday that Kyle and Littlefield had taken Routh to the range.

"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 said. “My heart is breaking. Our foundation, FITCO Cares, this country and most importantly, his wife Taya and their children, lost a dedicated father and husband, a lifelong patriot and an American hero.”

Cox called Kyle a hero and said, “Chris died doing what he filled his heart with passion - serving soldiers struggling with the fight to overcome PTSD.”

WATCH: CNN: Ex-Navy sniper, another military vet killed at Texas gun range

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