Eddie Routh, 25, accused of shooting Navy SEAL sniper Chris Kyle and his friend Chad Littleford Saturday, confessed to his sister and her husband about the crime, telling them he "traded his soul for a new truck," the affidavit says.
The document says the bodies of Kyle and Littleford were found at a shooting range at Rough Creek Lodge, 50 miles southwest of Fort Worth, Texas, with multiple gunshot wounds.
Investigators said Routh allegedly stole Kyle's Ford pickup truck and drove to his sister's home, telling her and her husband he had killed the two men, WFAA-TV, Dallas, reported..
Later Saturday, investigators found a semi-automatic handgun, believed to be the murder weapon, in Routh's home, WFAA reported.
Lancaster, Texas, police said Routh, an Iraq war veteran, threatened to kill himself and his family four months ago after learning his father intended to sell a family gun.
His mother said, "Eddie began arguing and stated he was going to blow his brains out," a police report of the Sept. 20, 2012, incident said.
Responding officers said Routh had post-traumatic stress disorder, the affidavit said, and placed him in protective custody before his hospitalization for a mental evaluation.