My take....... Under stress of a shooting situation, people, especially untrained people do strange things. Even trained people make strange decisions during a shooting situation. The only thing you can do is train and train right, and enough, so that your training kicks in as much as possible. Whatever you routinely do in training will come back to haunt you under stress. Why have dead cops been found with spent casings in their pockets after shooting the revolver empty and trying to reload? Because that's what they did when they trained at the range. Put the empties in their pocket. Instead of doing a fast reload, they took the time to do an unneccesary action. A combat shooter had been practicing rapid mag reloads for competition. He'd fire one or two rounds, then drop the mag and rapidly grab another and reload. Doing this repeatedly with about 6 mags on his belt. In a real life shoot out, he actually fired 2 rapid rounds, dropped the mag and reached for another, only to find there were no spares in the place he was reaching for. It was in his pocket. He survived the shooting after picking up the loaded mag off of the ground and re-engaging, but left the other loaded mag untouched in his pocket, because he forgot it was there.
The only reason I'm saying this, is because people will do strange things during a shoot out when they are trained, but even stranger things when they aren't well trained. This guy made a decision to go back and shoot the bad guy, I believe, because he felt the situation was still hot and things were still happening fast.
We can sit here and discuss, shoulda, coulda, woulda all day, but unless you were there or have been in a real shoot out, you don't know what you would have done, nor can you say this guy should have........
Now, Prediction. He will not be convicted of anything. He will be aquitted. Second, the little turds in the neighborhood will think twice before robbing him again or maybe other businesses in the area.
The Lesson, You cannot go into a business with a gun and a ski mask and expect things to go well. Life and robbery is not a damn video game. You have the right to get your ass shot off by someone in that business. The reset button won't work after that. The more this kind of thing happens, the fewer robberies we'll have. Your lesson. Train; train for real; train the way you would want to react; after you get the basics down, train at the same speed that it would happen in real life. FAST!!! Hope and pray for the best, and get it down in your mind, how you will react in certain situations.