Chris Kyle, a former US Navy SEAL sniper who was responsible for 160 kills during his career, was shot and killed with another man at a gun range on Saturday, according to the co-author of Mr Kyle's book.
A suspect has reportedly been arrested.
Mr Kyle, who wrote "American Sniper" about his military service from 1999 to 2009, and another man were found dead at the Rough Creek Lodge's shooting range, according to the Fort Worth Star- Telegram, quoting Erath County Sheriff Tommy Bryant. The second victim was not identified.
Loading article content
"It just comes as a shock and it's staggering to think that after all Chris has been through, that this is how he meets his end, because there are so many ways he could have been killed" in Iraq, said Scott McEwen, who wrote the book with Mr Kyle.
Rough Creek Lodge is in Glen Rose, Texas, about 50 miles south-west of Fort Worth. The range referred calls to the Erath County Sheriff's Office, but no-one there was immediately available for comment.
Mr Kyle served four combat tours of duty in Operation Iraqi Freedom and elsewhere, and won two Silver Stars and five Bronze Stars for bravery.
After leaving the Navy, he founded a firm that provided combat and weapons training to military, police, corporate and civilian clients,