The unidentified 77-year-old man was in a parking garage in the West Chesterfield neighborhood of Chicago at about 12:30 p.m. Saturday. The robber, who was also armed, pulled into the garage and demanded the elderly man fork over his possessions.
The man then produced his firearm and shot the robber in the head and chest, killing him, according to police.
Chicago police said the man had a valid Firearms Owner Identification Card and a Concealed Carry License. The Chicago Fire Department also confirmed he is a retired firefighter, Fox 32 reported.
An investigation has been launched into the matter.
Chicago has been struggling with an increase in crimes in recent months.
Chicago has had more murders and shootings so far this year than the three previous years, with 678 people murdered and 3,766 people shot as of Nov. 1. Data from 2020 between Jan. 1 and Oct. 31 shows 661 murders and 3,443 people shot, while data from the same time frame in 2019 shows 432 murders and 2,221 people shot.
The city has also had shoplifting issues in recent months, with repeated videos showing thieves taking thousands of dollars worth of luxury purses and makeup from stores in and near the city.