It is very unlikely that the dog is "Killing Deer". Male deer drop their horns in the spring. As to the skull,it is a crime in most states to possess human remains. CALL THE COP'S!!!
Bulls have horns, Bucks have antlers.
You sure possessing human remains is a crime?
Most art schools have skeletons, I think med schools do too.
I'm sure you can even buy the things mail order.
I've got a plastic skull that looks very real, 'course I'm not displaying it on a fence post, since I don't want it to get stolen.