The officer was seated in a car with three other people when they were ambushed by two unidentified men, police said. One man fired shots into the car, striking the officer and one other victim, before fleeing on foot.
The second victim, an unidentified man who is not a police officer, is in critical condition. Police say he is undergoing surgery and is expected to survive.
The two other people in the car, including another off-duty officer, were not injured.
The officer who was killed who has not yet been named, and who would have been with the department for two years in May had just finished a shift around 9 or 10 p.m. on Friday night. Police say he went to the nightclub purely for pleasure and they currently have no suspected motive for the shooting.
"We know that they did not have any sort of confrontations with anybody, they did not have any incidents that we believe would have provoked any sort of shooting," Police Deputy Supt. Anthony Riccio said during a press conference outside the hospital .
The officer and the shooter had "no conflict... no problems, no words exchanged, there was no robbery demand, no carjacking demand," Riccio said.
The shooter is still at large, though police say they do have a person of interest in custody.
"It's a very sad day, we're mourning the loss of yet another Chicago police officer," Fraternal Order of Police President Kevin Graham said.
The Chicago Police Department did not immediately return INSIDER's request for comment.
According to The Chicago Tribune , over 343 people have been shot in the city so far in 2019. This falls below the rate of shootings in the city for the previous three years.
