Thanks for the update on the wound and your assessment of shot placement.
When I saw the initial picture pulling the arrow shaft out of the body cavity it appeared that the shot would have been from the ground and the animal quartering hard toward or almost facing the hunter; bad choice on the part of the hunter.
However with the animal being hit at a downward angle as you describe, probably from a tree stand, the assumption that I and others on here made based on the little information available was incorrect....

Does it remain a BAD shot? Yes. Was there more for us to gain having not seen the wound and arrow path? I think so. These are big tough animals and the more we keep in mind their anatomy and our shot selections the more we can avoid not getting the quick clean kill that they deserve and we all strive for.

Again thanks and welcome to the site, ciao.