Catholic theology tells us that God is Sovereign over all things, and also that He does not force people to go against their free wills. He does, however, cause certain things to happen at times, and also that at other times He allows things to take their "natural" course without intervening. Thus, if He can make things happen, but does not always do so, the question we have to ask is this: Do we really know why things happen? Often we do not, but we can be certain of one thing: nothing happens that God does not either bring about, or merely allow to occur. There is not one rogue atom, one stray molecule, in all of creation, that can go against what God has decided to have happen.
That leads us to another fact: we can never say definitively whether God made something happen, or if He merely allowed it to do so. His involvement in events is clear, but the degree of involvement is not always clear. The problem comes about in a "scientific" age like ours, where people presume that science answers all those questions about the underlying cause of things (tornadoes, diseases, solar eclipses, etc.). When we fall into this prideful way of explaining the world, we often forget the hand of God. We say the earthquake was caused by tectonic plates (or something like that), and rarely ever ask the question of what God had to do with it. At the most, people will sometimes ask "where was God in all of this?" (as though the only thing God would ever do is stop an earthquake, but that He would never cause one!).
We should never be in the business of claiming we know that God caused some specific disaster because certain people did certain sins. Yet, if we exclude Him from the equation, then we are forgetting our faith. God is not a passive observer in creation, and He is also not using disaster and pain as a torture device. To ask why God allowed (or chose) something to happen, is not to presume that we have the specific answer, but it at least admits that God is involved. And, furthermore, the question opens us up to our Lord in a way that allows our hearts to receive an answer from Him; probably not a verbal answer, but since God is sovereign His answers are far more profound than mere words!