Good for him. Maybe not the best tactical choice, though; this could have easily ended very badly for the store owner, and I'm glad he's alright.

It probably wasn't a semi-auto shotgun, and if the robber had wanted to stick around he could have. Even if just for momentary revenge.

It is an important lesson, though, although not one you should necessarily rely on when your life is on the line; these robbers often don't want to kill people and, even armed, will hesitate or even wimp out completely if given any resistance. Again, not self defense advice, because if you run into the wrong guy resisting will just get you murdered. But often they aren't actually prepared to pull the trigger. Glad that was the case here, or this story could look very different.