Hard to say what happened to him but that last pic shows a cut in the tissue below the hide. Looks like a quartering away shot where the deer turned at the last min, or was too hard quartering at the time of the shot. Broadhead could have passed through the connective tissue between the ribcage and shoulder causing the lower 2/3rds of the shoulder to be cut loose. There isn't much holding the shoulder on right there to begin with.