A male suspect pulled out a gun and tried to rob another male passenger on a Blue Line train about 2:30 a.m., as the train was in the 500-block of South Pulaski Road in Garfield Park, according to CPD.
The victim fought off the man with the gun, and a shot went off and hit the train car window, police said.
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Police arrived on the nearest train platform and found the victim, who identified the suspect, as he was trying to walk away, CPD said.
The suspect was taken into custody, and a weapon was recovered.
No one was hurt in the incident, and nothing was stolen.
At 3:05 a.m., the CTA said trains were stopped due to police activity.
Trains resumed with delays about an hour later.
Charges are pending, as Area Four detectives investigate.