Oh my gosh this is really serious! You should talk to your dad about it. Tell him that you're worried about what you saw on the news and that it's weighing heavily on your conscience.
Tell him that he can't just brush this under the rug and the two of you need to look into this incident and see if the stories line up to the cause of death. But this could be scary for your dad so try to not to come across as though your accusing him. Just say that you're worried about him and that you two need to solve this together.
And take whatever steps you need to take if it happens to line up, which is between you two. Hopefully your dad learns to be more careful and not shoot on impulse anymore.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.