Poor thing died of lead poisoning.
They come into my yard after my kid's rabbits. The kids wanted baby rabbits so we one time ended up with a total of 30 rabbits.
My kids sure loved them, but then a band of raccoons came in while we were gone and wiped out almost 20 rabbits.
So now they are on the 'bad' list of my kids.
I've trapped several and relocated them, holy cow do they make a fuss about being in a cage! Since they didn't like that, and they didn't like swimming either, I figured I would help them with some extra minerals in their diets. Figured iron and zinc and such are put into vitamins and are supposedly good for you, so I figured they must be missing something out of their diets to keep coming around my house looking for my rabbits.
So I figured out it must be lead. Apparently this poor fellow overdosed on the stuff. I'll have to work on my proportions in the future.