pretty hard to tell what happened not being there. If I had to guess: your dad broke the front leg causing the buck to fall and possibly knocked him out as he fell down hill. Most likely went in far enough to hit the lung low, bubbles in the blood you found. Because the buck had so much trouble going up hill from the broken leg that he will turn to travel down hill for nearest water, thick cover to die. I think you can find him 100-150 yds from the last spot you saw him. Good luck on finding him tomorrow in good day light.
Last edited by Hunting Man; 12-17-2012 at 10:44 PM.