The nine-minute video from Eric Stillman's body camera showed the 34-year-old officer getting out of his squad car and running after Adam Toledo in an alley at 2:30 a.m. on March 29 in Little Village, a Mexican neighborhood on the city's West Side, Reuters reported.
The video then showed Stillman yelling "Stop" to Toledo before he caught up to him and ordered him to show his hands. Toledo appeared to raise his hands right before Stillman fired one shot and then ran to the boy as he fell to the ground.
"Shots fired, shots fired. Get an ambulance over here now," the police officer is heard saying in the video.
"Stay with me, stay with me" Stillman said. "Somebody bring the medical kit now!"
The Chicago Police Department said immediately following the incident that Toledo had a gun in his hand.
The release of the video was likely to rattle a nation already on edge over issues of policing, justice and race relations. Tensions were high on Thursday as a former suburban police officer in Minnesota appeared in court after she was charged in the killing last Sunday of a Black man during a traffic stop.
Hours earlier, the prosecution and defense rested their cases in the murder trial of former Minneapolis police officer Derek Chauvin, who is charged with the death of George Floyd, which ignited a wave of protests last year.
Chicago's Civilian Office of Police Accountability also released some 33 data files, including other police body-camera videos, footage from nearby security cameras, and documents related to the March 29 incident.
One of the documents identified Stillman, who has been on the force for six years, as the officer who shot and killed Toledo. He has been placed on administrative duty.
The Chicago Police Department also released part of the same video on its website on Thursday. The department placed an arrow on a still frame, pointing to what appeared to be a handgun in Toledo's right hand before Stillman opened fire.
"838 milliseconds between gun shown in hand and single shot," the police department said in a caption.
About five minutes and 30 seconds into the video, the officer shines a flashlight on a handgun feet from where officers worked frantically to save Toledo's life, giving him CPR.
RHM/PR