An off-duty sergeant in the Cook County Sheriff’s Office shot and killed one of three people who tried to rob him Monday night on the Far South Side, authorities said.



Police say three males tried to rob the sergeant as he was pumping gas at a Citgo in the 700 block of East 103rd Street shortly before 10 p.m., according to Chicago police and Cook County Sheriff’s spokesman Ben Breit.



The three demanded the sergeant’s wallet, which he gave to them. One of the men then pulled out a handgun and aimed it straight at the sergeant, according to Chicago police. The sergeant pulled out his own gun and shot the male in the head, killing him.



The two other males ran off and were not in custody early Tuesday, police said.



The sergeant was not injured. Breit said it's unlikely the sergeant's name or photo would be released immediately because he's a victim of a crime and the case was under investigation.