As to the original scenario. The criminal steps in front of shoppers and pulls a gun on the clerk. You are armed and have no doubt about what is happening. This is no confused situation and an armed robber has pulled a gun and has his back to other shoppers. He is crazy or at least very reckless. No telling what is next. Every situation is different and restraint is a good idea usually. In this case, smoke him from behind real quick.

Patriotism (and religion) is the last refuge of a scoundrel.
Jesus: "Take heed that no man deceive you."
Hebrew Roots Judaizer