Cicero police said two undercover officers working in the department's special operation division approached a vehicle after noticing it was illegally double-parked on the roadway.
Someone then fired shots at two officers near 35th Street and 61st Court around 12:45 a.m. One officer, shot in the back, was transported to Loyola Hospital in serious but stable condition, police said. The second officer was unharmed.
Some residents told ABC7 they heard what sounded like six gunshots.
"It looks like the offenders got away, but there was an undercover car that was shot up," Cicero resident Jennifer Donnell said.
Backup officers responded to the scene and took two people into custody as they tried to flee.
Video from the scene indicates that the investigation revolves around an SUV, which was surrounded by evidence markers on Saturday morning. That SUV's windows appears to have been shot out, and the rest of the vehicle is littered with what looks like bullet holes.
Police helicopters were over the scene at 61st Avenue and 35th Street at 5:30 a.m. Law enforcement officials from different agencies remained on the scene later into the morning, and were still there at 8 a.m.
The injured officer, a 29-year-old man, has served with the Cicero Police Department for just under five years.
Some neighborhood residents are on edge after the shooting.
"Scary, because I just moved here not too long ago," Cicero resident Aaron Salgado said. "My parents they think this area is very comfortable, safe."
The West Suburban Major Crimes Task Force is assisting in the investigation.
Cicero Police Supt. Thomas P. Boyle issued a statement, saying, "At this time, the connection between the suspects and the shooting is still under investigation. The officer struck in the back is receiving treatment at Loyola Hospital and is reported to be in serious but stable condition. The department will provide further updates as the officer's recovery progresses.
"This violent act underscores the dangers faced by law enforcement officers every day while they work to protect the community. The Cicero Police Department is committed to holding those responsible accountable and ensuring the safety of both police officers and residents. Anyone with information about the incident is encouraged to contact the Cicero Police Department Detective Division or the West Suburban Major Crimes Task Force to assist in the investigation."