Ok so lemme clear up a couple of things before people get too much in a twist.
(I got this stuff from a couple of Google searches and article in description)

1st: This happened in Brazil and from what I can tell, gun laws over there are fairly strict. You gotta register your gun, be 25 years old, and can only have it at your house. (There are exceptions, such as law enforcement.)
2nd: The customers in this scenario are all off-duty police officers which is why they all had guns.

3rd: When the robber came into the store with a gun out one of the officers shot him a couple of times and injured him. The robber collapsed and still went for his gun on the floor, so everyone else shot him again. I dunno if he's still alive or not, article isn't sure either.

via ytCropper