The world would be better off without some people. That being said, there's a big difference between the call of the void and true intent to act.

I can't imagine that any parent who saw their child murdered wouldn't at least entertain the thought of revenge. But I also see a profound power imbalance in your story. The powerful can act with impunity. Give the parent the power of reprisal and things start to look different. The child might have lived.

Perhaps there would be a bit less corruption and dishonesty in this world if there was a bit more fear of real consequences for ones actions.