Nowhere in the video does it show the robber on the floor. The burden of proof is on the state to demonstrate that he wasn’t a threat, not on the druggist. In the heat of the moment even a normally rational person could assume the perp to be a threat if he was indeed moving at all. The perp being unconcous is pure speculation from a DA and media that has already got this man convicted in their minds.
Also, the druggist had no way to know if the perp was armed or not. A reasonable person would assume (almost always correctly) that all participants in an armed robbery would be armed.
Everything you said in your post is correct except if the robber was such a threat, it would be strange for the druggist to turn his back to him as he walked by.
In the heat of the moment, a defender would certainly do all they could to stay alive at the moment. Too bad the druggist took the time to take out keys and unlock a drawer to change out firearms.
Forgetting the druggist for the time being, every instructor I had ever had made sure the class understood “you shoot until the threat is over”. I hope everyone who reads this post understands it’s important to stay alive and unhurt. It’s important to stay out of jail. It’s important to clear out of the risk of financial ruin.
You shoot until the threat is over. You might have to shoot the guy to the ground. You might be lucky one shot does the job. You don’t shoot twice and then evaluate. Let’s try it again. “You shoot until the threat is over”.