CHICAGO, Illinois - After a holiday weekend that was marred by at least 400 shootings that occurred across the U.S., Chicago Police say two ATF (Alcohol, Tobacco, Firearms and Explosives) agents and a Chicago police officer were shot early Wednesday morning during an undercover operation, CNN reports.

Chicago Police Department (CPD) Superintendent David Brown addressed the public regarding the shooting and said the three victims suffered non-life-threatening injuries.

One of the ATF agents was shot in the hand, and the other sustained gunshot wounds to the side/torso/arm area. 

The Chicago police officer was grazed in the back of the head by a bullet.

Brown explained, "Officers were fired upon from the street towards the on-ramp while they were in their car."

The three were conducting an undercover investigation and they were in one unmarked vehicle when they were fired upon.

The wounded officer is the 36th Chicago Police Department officer to have either sustained gunshot injuries or been targeted by gunfire, said Brown. 

One of the injured ATF agents is female and the other two victims are male. 

The suspect(s) remains at large at this time.

Chicago Mayor Lori Lightfoot addressed the recent uptick in violence in the city, saying, "I want you to know that we are doing absolutely everything that we can to stem the violence. I’ve met with many of you and I’ve heard your pain and anguish. I promise you, that I see you, that I hear you and that I feel you...We are seeing historic levels of violence, what more is it going to take?” 

Lightfoot continued, “And yet, we see people in Congress sitting on their hands and not doing anything.”

The Mayor was scheduled to meet with President Joe Biden Wednesday, which is when the police officer and two ATF agents were shot.