Without the audio, we don't know what the perp said or what triggered the officer to go into combat mode.
Perp: "Gim'me the money in the register." Perp turns left, takes a step and looks out the way he came in.
Officer: "Freeze! Police!" The perp turns toward the officer with something (weapon?) in left hand. *Bang*
If I were there as a civilian with a CCW, I would have done it differently. I'm not saying that the officer was wrong. I'm saying that CCW holders are not police. I would have also told the perp, "Freeze or I will shoot!" Then he would have turned and re-assessed the situation. He might have run. Threat over. Or he might have surrendered. Or he might have attacked. In which case, I would have shot also. But it would be the prep's choice to escalate.