Is it legal for a cashier to shoot a robber at a gas station if they're holding said cashier at gunpoint?

This is just out of curiosity. I don't work at a gas station and there hasn't been a robbery. I was just watching a show on Netflix when the cashier shot the robber. He had a small gun holding her at gunpoint, then she took out a large gun and said, "Drop it or I'll shoot." Then she shot him... show more This is just out of curiosity. I don't work at a gas station and there hasn't been a robbery.

I was just watching a show on Netflix when the cashier shot the robber. He had a small gun holding her at gunpoint, then she took out a large gun and said, "Drop it or I'll shoot."

Then she shot him and I was like, "Is the even legal?"

It's been making me think... When is it okay to kill a bad guy or a murderer and when is it not?
5 answers 5