I would not take that shot, but the claim was one lung, and I bet it got some of the diaphragm too, which would cause the lungs to stop working and the blood from the mouth. Another possibility of what happened was that the deer was quatering away, pretty steeply, then the deer turned its head to scratch its back w/ its teeth like they do or look behind it, but turned its front enough to show some vitals, then the shooter(new hunter)thought he had a shot, but hit a couple inched back, causing that steep angle. These 2 pics show kinda what I'm talking about, but imagine them turned a little more. to a new hunter that may look like a good shot.
http://i49.photobucket.com/albums/f288/zdeerslayer/roedeer.jpg

http://i49.photobucket.com/albums/f288/zdeerslayer/deer1.jpg