No it is not "depending on the situation." To me that means more than just the difference between ending a threat and murdering an innocent. The entire reason it is okay when someone is a threat is based on the premise that murder is always wrong. So that isn't really a case of depending on the situation. That's a case of being forced to defend the innocent against the guilty. You don't kill because of the situation. You defend yourself or someone else. That's a big difference.
So it is ok to kill, when one is forced to end a threat. How is that not dependent upon a situation, a threatening situation? I realise the difference, but the right or wrong of it really is dependent upon something. Anyway, I'm leaving, thanks.