Genie says, "A person who will deliberately inflict pain on another sentient being--be it a possum, a cat, a rabbit, or whatever--is potentially a threat to us human types, too." That's a fact. Weepiper, be careful that your vandal doesn't break a bottle over your head in the future. And that is no joke. I'm concerned for your own safety as well as for the safety of your kitties.

If you haven't reported this incident to the police yet, you should. And if you still have those pieces of glass, give them to the police so they can try to lift fingerprints from the pieces. The yard should be checked for shoeprints, too. If it's too late for any of that, bear it in mind in case there's a repeat of this incident, or a similar one.