Footage showed him reaching into the car. I've no knowledge of police procedure. If a suspect makes a sudden movement to retrieve some unknown item in a hidden area, does a weapon have to be visible before a responding officer opens fire? My guess is that these officers would have had a split second to respond, if he pulled out a gun.
But they would know that there was a danger of injury or death to themselves or a bystander and then deadly force would be warranted. But now if there is a chance that there might be a chance of injury or death to the officer of bystander it's blow them away time.