STEPHENVILLE — A man called "America's deadliest sniper" survived four tours of duty fighting in Iraq's bloodiest battles.
But former Navy SEAL Chris Kyle was gunned down along with a friend at a Glen Rose gun range on Saturday afternoon.
Investigators say the suspect was a former Marine they were trying to help.
The unanswered question is: What made Eddie Routh snap?
Routh was among friends at the Rough Creek Lodge gun range as a form of therapy to help with post-traumatic stress after years in the military.
Authorities said the former Marine didn't surrender easily. Routh tried to escape after being tracked tracked to his mother's home in Lancaster on Saturday night.
"We had no idea what was going on, and then — all of a sudden — the truck just races down the street," said witness Jan Gallagher.
After a brief chase, police arrested the 25-year-old, nearly 100 miles from the sprawling Erath County ranch resort where Kyle and Chad Littlefield, 35, were slain.
During target practice, police say Routh — for reasons not yet explained — turned his semi-automatic handgun on his friends.
"It's the answer we obviously want to get, but as of right now he has made no comments as to why," said Erath County Sheriff's Department Capt. Jason Upshaw.
Kyle and Little field had been treating Routh to a day on the range to help him deal with his post-traumatic stress after years of fighting in Iraq. Investigators said the idea was hatched by Routh's mother.
"She may have reached out to Mr. Kyle to try and help her son," said Erath County Sheriff Tommy Bryant. "We kind of have an idea maybe that's why they were at the range for some type of therapy that Mr. Kyle assists people with."
Kyle, well-known in military circles for being the deadliest sharpshooter, was also a best-selling author.
Since retiring, the 38-year-old devoted his life to helping fellow veterans deal with post-traumatic stress.
Kyle himself had survived years of war... the worst of the battlefield... only to fall close to home trying to help a comrade.
"We lost two American heroes," Upshaw said. "My heart goes out to the family, their friends and loved ones. We suffered a loss yesterday."
Chris Kyle is being hailed as a national hero. He killed so many enemy in the Iraq war that insurgents once put a bounty on his head.
His alleged killer now sits in a jail cell in Stephenville facing two counts of capital murder. Bond was set at $3 million.
The Rough Creek Lodge and Resort where the shootings took place spans 11,000 acres, located about 10 miles west of Glen Rose.
The facility offers lodging, conference space, and recreation areas. Guards were at the front gate on Sunday.
Officials would not specify where the shooting took place, but News 8 found investigators at a gun range far away from the main buildings.
Chris Kyle's service record includes more than 150 "kill shots," two Silver Stars and five Bronze Stars during his four tours in Iraq.