Chris Kyle, a former top Navy SEAL sniper, was shot to death this weekend by a fellow veteran. Authorities believe the suspect was suffering from post-traumatic stress disorder.
Known as America's top shot, Kyle served four tours of duty in Iraq. When he came home he tried to help fellow vets suffering from PTSD.
The killing, authorities say, points to the tough battle soldiers face when they return home.
"All of a sudden you don't have no identity, and you have to learn a whole new way to act," Kyle explained on Guns.com.
Authorities found Kyle's body, along with a friend's, at a shooting range in Texas.
"We have lost more than we can replace," American Sniper co-author Scott McEwen told ABC News in a statement.
"Chris was a patriot, a great father, and a true supporter of this country and its ideals," he said. "This is a tragedy for all of us," McEwen said. "I send my deepest prayers and thoughts to his wife and two children."
Authorities have charged Marine veteran Eddie Ray Ruth, 25, with both deaths.
"He is charged with two capital murders, held on $3 million bond," Erath County, Texas, Sheriff Tommy Bryant said.
Ruth is a former Marine believed to suffer from PTSD. Investigators say Kyle was trying to help him. The former SEAL's death comes as the military is under increased pressure to help returning veterans.
A new study by Robert Bossarte, a researcher with the Dept. of Veterans Affairs, shows 22 veterans take their lives every day in America. Last year, 325 troops died by suicide -- more than the number of soldiers who died in Afghanistan.
Meanwhile, experts are still figuring out how to best treat the disorder.
"We are in the dark in our ability to treat post-traumatic stress to a level that we can guarantee most individuals who have it can recover from it," U.S. Army Gen. Pete Chiarelli said.
On Monday, the secretary of the Army will visit joint base Lewis McChord after complaints that Army doctors changed PTSD diagnoses to other conditions that cost less to treat.
New research shows the suicide rate in the country is going up, and veterans are a part of it. Of special concern: the majority of suicides are committed by men age 50 and older.