The FBI is investigating a controversial police shooting at a Chicago transit station that was captured on camera.

The witness video shows a struggle between a man and two Chicago police officers on Friday. The man was shot twice, leaving him in critical but stable condition.

There are multiple investigations into why shots were fired – and an expert told "CBS This Morning" the officer was not justified in pulling out their gun in the first place, reports national correspondent Jericka Duncan.

On the witness video, Chicago police officers can be heard telling the man more than a dozen times to stop after they say he allegedly moved illegally between train cars, which is punishable by a fine but is not a felony.

The FBI is investigating an incident at a Chicago transit station in which a man resisting police officers was shot twice. CBS News

The female officer appears to use a taser on the man. Then you hear the male officer say, "Shoot him."

A gunshot rings out.

The video shows the man try to go up an escalator – and that's when you hear a second shot.

The man's attorney says the 33-year-old was shot in the chest and buttocks.

Charges against him were dropped, but investigators say they're considering "possible criminal charges" against the officers.

"We are extremely concerned and have significant questions about the incident," said deputy superintendent of Chicago Police Barbara West.

CBS News security and law enforcement analyst Paul Viollis reviewed the nearly five minutes of witness video. He said this shooting never should have happened.

"Based on police procedure, based on use of force, based on the way police are trained, it did not appear to be imminent fear to their lives or imminent risk to the public, which would have justified deadly physical force," Viollis said.

Both officers are on paid administrative duty during the investigation.

The Chicago Police Department issued a statement saying it is not rushing to judgment, but is cooperating with the independent investigations. The Fraternal Order of Police said the city should not be commenting until all the facts are gathered.