If you believe that after this life you will stand before God, you might have a conversation with Him similar to this:
You: Why did you allow ___ (fill in the blank) to happen?
God: Why didn’t you do something about it?
You: Because you didn’t do anything to help.
God: You just answered your own question.
We are instruments of God. If we stand idly by and watch something bad happen, thinking that God will intervene, we are not seeing our purpose… which is to try and stop a bad thing.