I'll start off by saying I think it was awesome he was there, armed, and mentally prepared to shoot.
NOW.... for my own educational purposes.... can we break the scenario down? I like to run shoot/don't shoot scenarios through my head. Here's how I see it:
The first shot was justified since there was obviously a threat to the shooter's life (the robber pointed his gun at the shooter) as well as extreme risk of threat to the other people in the room. I will say the lady standing behind the robber was damned lucky she didn't get hit.
I would say shot 2 COULD be justifiable since the robber still had a gun in his hand, and had only begun to indicate he might flee.
Shots 3, 4 and 5 were at a fleeing suspect. Were they legitimate?
Shot 6 was a VERY poor decision in my opinion. It was at a fleeing suspect, who was already out the door. On top of that, there was no time on the shooter's part to verify a clear background.
Like I said, I'm glad he was there, and glad he shot. I would have been happier had both robbers ended up face down in a pool of blood, but we can't win them all.