Body camera footage of the police killing of 13-year-old Adam Toledo appears to show an officer firing a single round into his chest less than a second after he turns around with his hands up.
It does not appear in the video that Adam was holding a weapon when he turned around, and his hands were up.
The teenager was shot and killed in an alleyway in Chicago in the early hours of 29 March.
The video footage was released Thursday by Chicago’s Civilian Office of Police Accountability. Adam’s family viewed it on Wednesday.
During a press conference on Thursday, city mayor Lori Lightfoot said she watched the video and called it “excruciating” while holding back tears.
Adeena Weiss Ortiz, an attorney for Adam’s family, said: “At the time Adam was shot, he did not have a gun.”
She added: “That child complied. Adam complied with the officer’s request. The officer saw his hands were up and he pulled the trigger.”
The city’s police force has prepared for protests in the wake of the video’s release. Both Ms Lightfoot and Adam’s family have called for any demonstrations to be peaceful.
In a joint statement, Adam’s family and the mayor said: “We acknowledge that the release of this video is the first step in the process toward the healing of the family, the community and our city.
“We understand that the release of this video will be incredibly painful and elicit an emotional response to all who view it, and we ask that people express themselves peacefully.”
The shooting came in the wake of a chase by police of Adam Toledo and Ruben Roman, 21, after officers were called following reports of shots being fired near by.
The bodycam footage shows a police officer running down an alley shouting: “Freeze stop! Stop right f***ing now! Hey show me your f***ing hands! Drop it, drop it.”
As the boy turns round with his hands raised, the officer fires once. The teenager falls to the ground and the officer runs over to him and bends down, shouting “look at me, look at me, look at me – you all right?”, and “stay with me, stay with me”, as he lifts his shirt to find the wound and calls for medical support.
As other officers arrive and try to save Toledo, the officer who shot him walks away from the scene and appears to be crying. Shortly after, another officer calls over the police radio and instructs officers at the scene to turn off their cameras.
Mr Roman was arrested at the scene.