You mean like the bodycam video that it's in the article? The one that clearly shows at least one of them wearing a vest that has 'POLICE' written on it while they repeatedly tell him to unlock and open the door? and after being told multiple times to unlock and open the door, saying he will, so the cops on the drivers side all back off to let him out and then he starts blasting at the one on the passenger side?
There was absolutely no confusion at the point when he started shooting that they were cops.
https://abc7chicago.com/dexter-reed-chicago-police-shooting-body-camera-video-copa/14637195/
More information here, from the video narration:
The 26 year old was already facing illegal gun charges and if the cops found the gun he'd be going back to jail. He didn't shoot in self defence. He shot because he was a criminal afraid to go back to jail.