Here are more details on the incident - and it doesn't appear to be the way Police Superintendent McCarthy or the news media described initially:
According to Cook County Assistant State's Attorney John Dillon, Colon was the driver during the attack, while Clay and a third man -- who did not appear in court today -- donned masks and entered the store.
When they got inside M&M Quick Foods, Lewis announced he was a police officer, at which point Clay and the third man opened fire, Dillon said in court.
Lewis was able to fire one shot before he was struck by a bullet to the abdomen and three shots to the back, Dillon said. Bullet fragments also struck a store employee, according to the prosecutor.
I think a police officer responds to this different than I would in that maybe it's second nature for a police officer to shout "Police!"
I don't know if he did that simultaneously while drawing or it happened sequentially, but I'm guessing that when he identified himself he drew fire.