(CBS) – Surveillance video of a Chicago police officer fatally shooting suspect Cedrick Chatman prompted one misconduct investigator to determine it wasn’t justified.

It’s a decision that cost Lorenzo Davis his job, he says.

CBS 2’s Dorothy Tucker gets Davis’ take on the tape on the day it was released publicly, three years later.

“The shooting was not justified,” says Davis, a former investigator with the Independent Police Review Authority.

He says he reached that conclusion after he and his team viewed three tapes of 17-year-old Chatman running from police after allegedly stealing a car in January 2013. Davis says much of video is not clear, but he and his team watched all of them numerous times.

Chicago Police Officer Kevin Fry shot Chatman, but Davis says the cop could have chased him instead of shooting. Davis also considered Fry interview, where he says the officer changed his story, or “hedged,” on whether the suspect turn toward him during the pursuit.

Despite a determination that the shooting was not justified, Davis says his superiors wanted him to change his ruling. When he refused, he says he was fired. Another investigator concluded the shooting was justified — a ruling that still stands one that Davis doesn’t like.

Fry and another officer involved in the incident, Lou Toth, are being represented by attorney Andy Hale. Hale says the videos support officers’ belief that Chatman was armed as he was running from the officers.

Dorothy Tucker