It happened Friday afternoon in the city's Washington Heights neighborhood near 96th and Princeton.
Independent Police Review Authority spokesman Larry Merritt said his department was notified just before 1 p.m. of the earlier shooting involving an off-duty police officer in the 9600 block of South Princeton Avenue.
Fraternal Order of Police spokesman Pat Camden defended the officer's actions, saying the 33-year-old officer was with his 7-year-old daughter at their home when someone rang the doorbell about noon.
The officer saw a van parked in front of his house but did not open the door, assuming the visitor was a solicitor, Camden said. He then heard someone trying to pry open the front door and saw the van outside pulling up to the side of the house, he said.
The officer sent his daughter to her bedroom and called 911 before going outside and through the side door, finding two men in front of his house as well as another driving the van, Camden said.
One man ran away northbound on Princeton, and the other ran toward the officer on his way into the van, Camden said.
As the man was getting into the van, he pointed a gun at the off-duty officer, who shot the man in his left shoulder, Camden said. The van then led police on a chase before crashing near the intersection of South Yale Avenue and West 89th Street, he said.
The man shot by the officer was taken to Advocate Christ Medical Center in serious condition, and the driver of the van was arrested, Camden said. The third man who ran away is still at large. Some streets in the vicinity of 89th and Yale were closed Friday afternoon as police searched the area.
The officer and his daughter were unharmed.
Chicago police are investigating. Anyone with information should call Area South Detectives at 312-747-8271.
The Sun-Times Media Wire contributed to this report.