“How can you trust God after an event like this? The Christian answer to issues of suffering and tragedy always has to do with the Cross.
Imagine you are an admirer and companion of Jesus Christ during his ministry.
He is such a powerful worker of miracles that disease and hunger are almost banished from the countryside when he is present. He is such a powerful teacher and spiritual guide that thousands of people hear him gladly and get hope. Then suddenly this man who is the one to help the whole country is cruelly, unjustly cut off in the very midst of his life.
What if you stood at the foot of the cross in front of this apparently senseless act of violence and tragic waste of life, and you said, 'I can never, ever trust God again after an event like this!' And what if you went home and completely renounced all belief in God saying, 'This proves that God is either a monster or indifferent or he doesn't exist'?  If you did that, you would have been missing the greatest act of God's love and redemption in history.”
~ Tim Keller, Reflections on September 11