The officer, who was apparently off-duty at the time, was attacked in the 4700-block of South Wentworth near the exit ramp of the northbound Dan Ryan Expressway at about 2:30 p.m.
Moments after the attack, Chicago Fire Department paramedics found the wounded officer at 43rd and Wentworth.
The 43-year-old officer was transported in good condition to Northwestern Memorial Hospital. Unconfirmed reports say he suffered a graze wound to the head.
Investigators have yet to confirm many of the details as they continue to sift through the evidence. It is still unclear if a weapon was recovered from the scene or if a suspect or suspects are in custody. It is also unclear if there was another vehicle involved in the incident and if there is a possible description or license plate for that vehicle.
Police say that the investigation is ongoing.