God is absolutely sovereign over his creation. Nothing can happen unless God allows it. God controls every lightning bolt and the path of every tornado.
(Isaiah 45:7 NIV) I form the light and create darkness, I bring prosperity and create disaster; I, the LORD, do all these things.
(Amos 3:6 NIV) When a trumpet sounds in a city, do not the people tremble? When disaster comes to a city, has not the LORD caused it?
God does things for his own purposes. God doesn't have to answer to us for what he does. We have no right to judge God or God's actions.
RE: Why does bad stuff happen