The man was walking in the 9200 block of South St. Lawrence Avenue around 7 a.m. when someone grabbed him from behind, Chicago police said.
During the struggle, the man was shot while he attempted to grab his gun, police said.
He was struck in the chest and transported to the University of Chicago Medical Center in critical condition, according to officials.
Police said a weapon was recovered at the scene.
No one is in custody and Area Two detectives were investigating.