ShotSpotters listen for the sound of gunfire, then send alerts to officers with specific locations.
Critics say the system, known as ShotSpotter, doesn't lead to enough crimes being solved.
Investigators said witnesses helped identify the suspect's car with the help of a license plate reader, which is another piece of technology they use. In a recorded ShotSpotter incident from last week, police said they were able to react quickly enough to find the victim still alive in his car, along with shell casings from two weapons.
The company responded to questions raised about that OIG report saying,"The Chicago Police Department continually describes ShotSpotter as an important part of their operations. The OIG report did not specifically suggest that ShotSpotter alerts are not indicative of actual gunfire whether or not a police report is filed or physical evidence is recovered.
"It's the new stop and frisk policy here in Chicago," said Jose Manuel Almanza Jr., with the Stop ShotSpotter Coalition.