Evil is not a “thing”. It does not have being, and it does not “exist”. Evil is a privation of something that should be present but is not. This is the point that tugbaby was trying to make. We might speak of evil existing, but this is only a loose manner of speaking. A privation is rather something else not existing that should exist, so evil is the absence of something.
This is an absolutely critical point. It was made brilliantly by St. Augustine and has been a cornerstone of Catholic philosophy ever since.
While a privation cannot be made, it can at least be caused, so there is still a sense in which it is worth asking, did God cause evil? To answer this, we must first make a distinction between moral evil, which God never causes, and physical evil, which God does cause. For God to will or cause moral evil would be a direct contradition of His Nature. It would be saying that something always right does some things wrong. It doesn’t even make logical sense that such a thing would be possible. If God exists, He cannot will or cause evil, just as a circle cannot be square.
Physical evil is a kind of privation, but is not directly opposed to goodness itself. An example of physical evil is the lion killing the zebra. Does something “bad” happen when the zebra dies? Sort of, but not really. Did the lion do something wrong? No. Yet, it is still considered a physical evil because a zebra is meant to exist as a whole, and it is not good for the zebra to be ripped apart–it is down right bad for the zebra.
Moral evil is the result of man’s or the angels’ free will (yes angels have free will). We have the ability to chose a lesser good rather than a greater good which we are supposed to chose. Sin is not directly choosing something bad, but it is choosing a lesser good when there is another greater good that should have been chosen.
