Its awful isnt it. I can totally empathise with you as I had similarish happen with my cat. She was shot with an air rifle, numerous times, twice in the head. She did survive though, after lengthy op.
On another note, I know a lovely guy, he really is nice. When he was 15 he put a firework through someones porch letterbox. It was meant to scare the mean old lady that lived there, he had no idea her dog was there. He killed it, admittedly as soon as he knew he handed himself in, he couldnt live with it and is possibly why he is so nice now.
Maybe it wasnt intentional? Maybe they were just looking to blow a box up and create some noise? Im probably being a little optomistic but go to the papers and let them see how disgusted everyone is. They wont feel half as clever then.