Was slick. He ducked down behind the counter so he could draw his weapon without alerting the perp. Then, "came up firing" before the robber could recognize the development. The robber thought he was in control, but actually never had a chance. Got what he deserved. OORAH!
The robbers were STUUUUUPID. Even a half-brain would know the employees in a gun shop are likely carriers. Why would you try to hold up such a place when you know people inside are likely to have guns and know how to use them?
For the same reason, you shouldn't ever try to hold up a donut shop.
Donut shops usually have cops inside.... COPS HAVE GUNS! DUH!
Use your head. Jeezus Christ!