The Killeen Police Department is searching for the man involved in the shooting death of a security guard.

William Petty, 58, was killed Sunday morning after being shot at the Subway restaurant on 1100 Old FM 440. Police released Petty's identity on Monday afternoon. 

Officers say a male suspect wearing a ski mask entered the Subway when Petty, security guard on duty approached him.

Words were exchanged between the two but police say that during the argument the security guard was shot.

Employees and customers were in the restaurant at the time but no other injuries were reported.

Police describe the suspect as a black man, about 5'6" inches, wearing a dark gray sweatshirt, black shorts with red and white trim and white tennis shoes.