People on drugs in illegal possession of guns robbing are not rational, you shouldn't expect them to be.

Weird that there are no guns, because I'm pretty sure I read about a guy shooting up a shopping district and guns were used in Paris.

If the robber didn’t legally possess the gun how do you think a law against guns for everyone would prevent a criminal from breaking the law to possess one when they did so in this case and obviously don’t care about the law?

They can have a knife, you just have to be able to prove your life was in danger and you had no option to retreat.