The Iraq War veteran charged with killing a former Navy SEAL sniper and his friend on a Texas shooting range had been taken to a mental hospital twice in the past four months, police records show.

Eddie Ray Routh, 25, is charged with one count of capital murder and two counts of murder in the shooting deaths of Chris Kyle, author of the best-selling book "American Sniper," and his friend Chad Littlefield at a shooting range Saturday in Glen Rose.

He is on suicide watch in the Erath County Jail, where he's being held on $3 million bond (NZ$3.5 million), Sheriff Tommy Bryant said.

Routh was taken to a mental hospital on September 2 after threatening to kill his family and then commit suicide, according to police records in Lancaster, where Routh lives. Authorities found Routh walking nearby with no shirt and no shoes, and smelling of alcohol. Routh told authorities he was a Marine veteran who was suffering from post-traumatic stress disorder.

"Eddie stated he was hurting and that his family does not understand what he has been through," the report said.

Routh's mother told police that her son had been drinking and became upset when his father said he was going to sell his gun. She said Routh began arguing with them and said he was going to "blow his brains out."

Police took Routh to Green Oaks Hospital for psychiatric care.

Dallas police records show Routh was taken back to the same mental hospital in mid-January after a woman called police and said she feared for Routh's safety.

Routh, a member of the Marines Corps Reserve, appeared ready to assault jailers Sunday night when they entered his solitary confinement cell because he refused to return his food tray, Bryant said. After warnings, jailers used a stun gun once and then put Routh in a chair that restrains his arms and legs, Bryant said.

Bryant said Routh has an attorney but hasn't met with him at the jail in Stephenville, southwest of Fort Worth. Routh has not said anything to investigators, Bryant said.

Authorities say the three men arrived at the sprawling Rough Creek Lodge on Saturday afternoon, and a hunting guide discovered the bodies of Kyle and Littlefield about two hours later and called police. Bryant said Sunday that the men were shot more than once.

Routh then drove Kyle's pickup to his sister's house in Midlothian and told her that he killed two people, and she called police, Erath County Sheriff's Captain Jason Upshaw said Monday. Routh was arrested after a short police pursuit in Lancaster, near his home.

Attempts by The Associated Press to reach Routh's mother and sister were unsuccessful Monday.

Routh joined the Marines in 2006 and rose to the rank of corporal in 2010. His military specialty was small-arms technician, commonly known as an armorer. He had been stationed at Camp Lejeune, North Carolina, and served in Iraq from 2007-08 and in the Haiti disaster relief mission in 2010.

Travis Cox, director of FITCO Cares - the nonprofit that Kyle set up to give in-home fitness equipment to physically and emotionally wounded veterans - said he believes that Kyle and Littlefield were helping Routh work through PTSD.

Cox said Routh's mother may have asked Kyle to help her son, but Cox didn't know how Routh and Kyle knew each other. He said the shooting range event was not a FITCO session.

Lieutenant Commander Rorke Denver, who served with Kyle in Iraq in 2006, wasn't surprised that Kyle apparently used a shooting range to help someone with PTSD.

"For us, for warriors, that's a skill set that has become very familiar, very comfortable for us," said Denver, a lieutenant commander in a reserve SEAL team. "So I actually see it as kind of a perfect use of Chris' unique skill set and expertise of which he has very few peers."

Kyle, 38, left the Navy in 2009 after four tours of duty in Iraq, where he earned a reputation as one of the military's most lethal snipers. "American Sniper" was the No 3 seller of paperbacks and hardcovers on Amazon as of Monday, and the hardcover was out of stock. Littlefield, 35, was Kyle's friend, neighbor and "workout buddy," and also volunteered his time to work with veterans, Cox said.

- AP