Here's another way of looking at it. I don't mean those little round sugar-coated lumps you buy at the donut shop. I mean the hole itself. Donut holes are actually what's left when the middle is cut out of a donut. Same thing with a shadow.
Evil is like that.
Evil isn't like some black, gooey stuff floating around the universe that gloms onto people and causes them to do awful things. Evil is the absence of good, a privation of good, not a thing in itself. When God created the universe, he created everything good. He made a universe that was perfectly good. Everything was as it should be.