I'd have a little chat with one of your local wildlife officers. A sudden unexplained issue with any wildlife, whether it's disease related or may be due to rotten unsupervised kids that like to harrass critters, should be mentioned to them. Since you've bagged one, they might want to check it for BB pellets or the like as well as test it if that's their procedure. They might also just blow you off, but what's the harm in a phone call I figure.