Cat mutilations and killings! Why would a person do such a thing?

There have been a string of cat killings and mutilations around my city; a dozen cats have been killed or mutilated within the past three weeks, today I found a cat tail in my front yard and because it wasn't my cat it's going to be taken down as just a tip, it's a big story right now so the only people that seem interested is the media. We have called all the appropriate places; there seems to be not much that we could do. I don't expect to find answers here, I'm just angry and upset and don't know what else I could do. Why would somebody do this?