The Jews would have been justified in killing every German they could get their hands on if it could help stop the Holocaust.
A genocidal society has no right to claim the mercy of a civilian/soldier distinction. They do not recognize it themselves.
It is a horrible tragedy on a personal level. No one person has any power over the situation they find themselves in, but that is the brutal logic of war. Societies will feel less safe in engaging in targeting civilians if their own are subject to retaliation when they do so.