The shooting occurred at 92nd Street and South Stony Island Avenue.
Officers were conducting a traffic stop around 8:30 p.m. on a vehicle that was suspected of being involved in crimes in the area, Supt. Brown said at a news conference Wednesday night.
During the traffic investigation, officers became involved in an exchange of gunfire with occupants inside the vehicle.
A male officer was shot in the left leg. He suffered non-life-threatening injuries, and is listed in stable condition, Brown said.
A male offender was shot in the torso and wounded. The condition of the offender is not currently known.
A second person of interest is also in custody, Supt. Brown said.
"As far as we know now, it may change, but from what we know now, two occupants [were in] the vehicle," said Brown.
At least one gun was recovered from the suspect vehicle.
"At this point, all we have is this information," said Brown. "We need further investigation, interviews, video and witnesses to come forward for us to piece together how all of this transpired."
Supt. Brown did not provide the name of the officer injured or how many years the officer has been on the force.