who knows....is that spot on the back even an injury? I've seen lots of deer with healed over front legs, there's any number of things they can break them on...holes, barbwire, land funny or slip going down a bank.
a random speculation would be his foot was caught in a fence, and yotes started to get to him before he pulled free.... a more realistic guess would be car collision like others said.
Could be. That does look like a healed up bullet hole in his back. Also appears to have muscle atrophy in the left rear leg. Surprising his rack is still intact.
Any pictures in the daytime? I know I wouldn't be showing my backside until it was pitch dark if I was him.