The Chicago Civilian Office of Police Accountability, which investigates potential cases of police misconduct, released 17 body camera videos - including graphic video from the shooting officer's camera that shows Toledo being shot and lying motionless with blood on his chest and face.
The nine-minute video began by showing an unidentified police officer getting out of his squad auto and running after Adam Toledo in an alley at 2:30 a.m. on March 29 in Little Village, a neighborhood on the city's West Side.
John Catanzara, president of the Fraternal Order of Police, said the officer was justified because Toledo "still turned with a gun in his hand".
The 34-year-old white officer's bodycam footage shows him chasing Adam Toledo on foot down an alley for several seconds. Stop right f***ing now!
As the teen slows down, Stillman yells "Hands!" 'Show me your f***ing hands!
Once there, Stillman shoved Roman to the ground, body-cam video showed.
The footage continues as the officers seeks to administer first aid and waits for an ambulance crew to arrive.
"I don't think it matters whether Adam is a choir boy, whether he is involved in some other untoward activity - the fact of the matter is that he was walking in the street and he was shot unarmed", Adeena Weiss-Ortiz, the Toledo family attorney, told reporters.More news: United States expels Russian diplomats imposes new round of sanctions
"(Toledo) has a gun in his right hand.
"Simply put, we failed Adam", she said. "He turned around", she said.
The release of previous police shooting videos have sparked major protests in the city, including the 2014 shooting of black teen Laquan McDonald 16 times by a white officer.
The city's Civilian Office of Police Accountability (COPA) said it will release police body-worn camera footage on Thursday.
"The people of Chicago deserve answers about the events surrounding this tragic interaction", Colleen Connell, executive director of ACLU Illinois said in a statement.
"As a mom, this is not something you want children to see", Lightfoot said.
The man was arrested on a misdemeanour charge of resisting arrest.
Officer Stillman's footage shows him shining a light on a handgun on the ground near Adam after he shot him.More news: Father, son arrested in California in connection with Kristin Smart case
Before the video's release, some businesses in downtown Chicago's "Magnificent Mile" shopping district boarded up their windows.
In a statement released last week, the agency described it as "troubling video footage".
"It happens now that these circumstances are sitting next to each other", she said. The Toledo family issued a statement urging people to avoid violent protests.
Adam's family viewed it on Wednesday.
Both Ms Lightfoot and Adam's family have called for any demonstrations to be peaceful.
COPA also plans on releasing third-party video of the incident, ShotSpotter recordings, Office of Emergency Management and Communications transmissions, as well as use of force and arrest reports.
'The officer did everything he possibly could to the letter of the law and the guidelines of the Chicago Police Department'.
The Chicago Police Department has a long history of brutality and racism that has fomented mistrust among the city's many Black and Hispanic residents. The release of the videos of Adam's death just so happened to coincide with these preparations, Lightfoot said.More news: Paul Flores arrested in 1996 disappearance of Kristin Smart