Police said the 36-year-old victim was using an ATM in the 2300-block of West Madison Street around 3:20 a.m. Friday when the robber approached him from behind and demanded money.
The victim turned around and hit the suspect in the face. Police said that's when the robber took out a gun, pulled the trigger and ran away. The suspect did not get away with any money.
The victim was rushed to Stroger Hospital, where he is listed in serious condition.
Police did not give a description of the suspect. No one is in custody. Area Central detectives are investigating.