A Chicago police officer exchanged gunfire while conducting surveillance in Calumet Heights Wednesday evening, according to authorities.
Police on Monday said a person arrested after the incident was released without charges.
The officer and a partner were in an undercover car around 7:30 p.m. in the 2600 Block of East 92nd Street, conducting surveillance on another car in connection with an ongoing investigation, police said in a statement.
Three people, described only as males, got into the car and the front passenger then fired at the officers, according to police. One of the officers fired back. No one was injured, police said.
One of the males was placed in custody, and a weapon was recovered at the scene, according to police.
Officers are still looking for the other two, police said. They were wearing surgical masks and black clothing, according to police.
The two officers were taken to the University of Chicago Medical Center for observation, police said.
The Civilian Office of Police Accountability will investigate the incident. Both officers will be placed on routine administrative duties for 30 days.