Disturbing bodycam footage was released this week by Chicago police, showing the boy appearing to drop a handgun and raising his hands less than second before he was shot by the officer.
A still frame taken from Mr Stillman's body camera footage showed that the 13-year-old was not holding anything and had his hands up when the officer shot him once in the chest at about 3am on 29 March.
Small protests were held over the shooting on Thursday evening around Chicago, not long after the city’s mayor urged the public to remain calm.
“We live in a city that is traumatised by a long history of police violence and misconduct,” Mayor Lori Lightfoot said.
“So while we don't have enough information to be the judge and jury of this particular situation, it is certainly understandable why so many of our residents are feeling that all too familiar surge of outrage and pain.
“It is even clearer that trust between our community and law enforcement is far from healed and remains badly broken.”
Here’s what we know so far about the officer involved:
The Chicago Police Department does not typically release the names of officers involved in such shootings this early into an investigation but Mr Stillman’s details were listed in the investigations reports COPA released on Thursday.
He is a 34-year-old white man who had been assigned as a patrol officer to the city’s Ogden (10th) District, an area that includes Little Village where the shooting took place, according to CBS Chicago.
The local news channel found that over a five-year period ending in the summer of 2020, Mr Stillman had never shot anyone and had nine “use of force” reports, of which only one involved any sort of weapon (a baton).
Adeena Weiss-Ortiz, an attorney for Adam Toledo's family, noted that having looked into the officer’s past, she found “no prior discipline, no prior events”.
In the footage released by the police force, Mr Stillman can be seen radioing for an ambulance for the boy and administering CPR as other officers arrive.
He has been placed on administrative duty while an inquiry is conducted into whether he followed proper procedure on use of force during the incident.
Police have said Adam had a handgun on him before the shooting, with footage from Mr Stillman’s bodycam showing the officer shining a light on a weapon on the ground near where the boy was shot.
Ms Weiss-Ortiz has argued that it is irrelevant whether the 13-year-old was holding a gun before he turned towards the officer as he had already dropped it and was unarmed at the time of shooting.
“If he had a gun, he tossed it,” she said. “The officer said: 'Show me your hands.' He complied. He turned around.”
She also told a news conference following the release of the footage: “I don't know if the officer had enough time or not [to know Adam was unarmed].
“All I know is the officer is trained to not shoot an unarmed individual.”
The shooting has come at a sensitive time amid the ongoing trial of former officer Derek Chauvin in Minneapolis over the death of George Floyd and the recent police killing of another black man, Daunte Wright, in the city.