The injured officer was transported to Northwestern Memorial Hospital where he was listed in good condition late Saturday. He is expected to survive.
Police are not releasing the officer's name, but authorities say he is a 10-year veteran of the force and a 3rd District police officer.
The shooting happened around 7 p.m. Saturday evening. Police say two officers had just finished speaking to a man who had been acting strangely. The officers were walking back to their squad car when the man opened fire, police say.
"One officer, a 10-year veteran of the Chicago Police Department was struck twice. He was hit in the vest and in the shoulder. His partner, who was not struck, returned fire. It is unknown at this time if the offender was struck," said Chicago Police Dept. Supt. Jody Weis.
The wounded offficer will likely be released from the hospital by Sunday morning. Relatives were scene arriving at Northwestern Memorial Saturday evening.
"He is doing terrific. His parents were with him His family is with him. He is in a good place," Weis said.
Authorities say the suspect may still be armed and is described as a Hispanic male, heavyset, wearing a white jacket with green stripes and jeans. Police say he fled the scene and may be driving a 2002 gold-colored Saturn with Illinois license plate number 648 8550.
"This was a relatively routine stop. It was viewed by officers. But it just shows how even the most routine incident can turn into a deadly encounter. Fortunately, for this one, the officer's vest worked," said Weis.
Following the shooting, officers were scene combing nearby yards and alleys with automatic weapons.
Neighbors say crime is a near-daily occurrence in the area where the officer was shot.
Police say, since January, at least seven CPD officers have been shot. Three of those officers died from their wounds. Saturday night's incident, they say, is an indication of the dangers officers face every day.