The office said Chicago police asked for a review of the shooting in the underground station at West Grand Avenue and North State Street in the city's River North neighborhood.
The state's attorney's office said it couldn't comment further while an investigation is underway.
The shooting occurred after police said mass transit officers on a Red Line train saw a man moving from train car to train car, which is against a city ordinance. The officers made contact with the man, and attempted to arrest him shortly before 4:30 p.m.
A struggle ensued on the Grand platform as the man resisted arrest, police said. Officers then deployed their Tasers.
As the man continued to resist, police said one of the officers shot twice. Other mass transit officers came to render aid, and the man was taken to Northwestern Memorial Hospital.
Police said Saturday that the man had surgery and remains in critical condition.
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A witness recorded a video showing the struggle, with a man held on the ground by two police officers.
"He was resisting but he was not violent, as far as I could see, and he was unarmed," said Michael McDunnah, who shot the video.
Roughly two minutes pass with police pinning the man to the ground. The female officer called for backup as the man on the ground refused to give up.
"At some point the male officer said 'shoot him,'" McDunnah said. "The female officer at that point, I think, pulled out her mace and maced him in the face."
That's when the situation appears to escalate. The man staggers to his feet, freshly maced.
"That was the point at which the female officer fired her weapon," said McDunnah.
McDunnah said his view was obstructed by the officer at this point.
"I could not see if it hit him," he said. "He sort of lurched. It looked like it did hit him."
And from there the video shows the man, and officers, sprinting up the escalator and another gunshot.
Another witness recorded officers tending to the man after he'd been shot, before taking him away in an ambulance.
Mayor Lori Lightfoot called the witness video shared on social media "extremely disturbing" and said "the actions by these officers are deeply concerning."
I have viewed the widely shared footage depicting the police-involved shooting at the CTA station. With the strong caveat that one perspective does not depict the entirety of the incident, the video is extremely disturbing and the actions by these officers are deeply concerning.— Mayor Lori Lightfoot (@chicagosmayor) February 29, 2020
"The incident is being independently investigated by the Civilian Office of Police Accountability to ensure the public gains a complete picture of what happened," Lightfoot said. "Furthermore, to ensure full transparency and accountability, I support Superintendent Beck's decision to contact the State's Attorney due to the potential criminal nature of this incident."
Chicago police have also launched an internal investigation into the shooting.