If you look at the news video around 1:08, you see the two guys in darker clothing standing in front of the glass that Mike shot out of, while the guy at the register still had his gun drawn and was being handed money from the clerk at the register. As soon as you see the shots fired, the guy at the register turns and runs. The clerk at the register should thank his lucky stars that the robber with the gun reacted by running away, and not pulling the trigger on the clerk.

The reality of it is probably just barely starting to settle in now...situations like that could have gone the other way just as fast.