Ubiquitin, he was sent to protect Am Yisrael. Part of protecting Am Yisrael is killing terrorists.
I am behind him 100%. A go’el hadam is allowed to kill a Jew who accidentally killed his relative. We should certainly be allowed to kill our enemies who are out to destroy us and kill us deliberately.
Who knows how many lives he saved? He will receive a tremendous schar in Olam Haba for his actions.
And he certainly did not deserve to be convicted of manslaughter.
Please note: I do not know whether or not l’chatchila a person in such a situation should act as he did or not. One would have to ask a sheilah. But I think it was completely understandable, and having done it, I certainly don’t think he should be condemned for his actions and he certainly should not be treated like a murderer.