I hear that. But I do see that with the one guy reaching into the vehicle in an attempt to open the door after he found it locked the first time, the guy may also have been worried about his coworker and whether that coworker might be dragged. Split second later things change... I also wonder if the gun went off because he was hit, not because he meant to pull the trigger.
It is clear that she knew they were law enforcement, you can hear him give a lawful order, in a way that didn't seem to be an attempt to deescalate.
I'd like to see the first reaction be towards less than lethal weapons, but if we are going with "what did the officer think"... It seems that he thought there were lives in danger and that we would have a very difficult time proving he did not, and if we use the same standard we always use for law enforcement... I think they'll find this justified.