Well there is obviously a difference between the attacker and the one responding to it.
If two people break into my house, kill my husband, and as a response I kill then both. Am I worse as it’s 2-1 murder-wise?
Makes no sense what you said. The situation is more akin to having someone kill your husband, and you going into the street and murdering as many people you can in the town next door, who have nothing to do with it. That's called senseless revenge.