He was identified to the Cook County Medical Examiner's Office as Charles K. Macklin, authorities said.
A 45-year-old man, who fire officials confirmed is an off-duty CFD lieutenant, left his vehicle running in the 1400-block of north Lockwood Avenue in Chicago's North Austin neighborhood, police said.
Around 9:30 a.m., police said Macklin got into the vehicle. The lieutenant fired shots at the teen in an attempt to stop the suspect from running him over, police said.
Macklin sustained a gunshot wound to the chest and was transported to West Suburban Medical Center, where he was pronounced dead at 9:33 a.m. An autopsy is scheduled for Tuesday.
The lieutenant has a valid concealed-carry license and firearm owners' identification card, police said.
Area North detectives are investigating the shooting.
The Sun-Times Media Wire contributed to this report.