what in the hell always causing eyes to pop out during some deaths!!!???
It's fairly common in head shots because the hot gasses from the gun enter and then expand inside the cranium. It might also be a weird environmental factor that made him decomp in a funny way.
Don't worry.... if you've seen one zombie shot in the head...you've seen them all. Just imagine a little kid's toy gun... tricked out with a little soderd on iron, and that's what the gun looks like.