I should have asked the questions I wanted to at first, but then decided to let the post propagate a bit.
1.) What length and color of hair did you find at the impact scene?
2.) Was there any tallow on the shaft?
I don't think the arrow hit the opposite shoulder, because then we're talking organ damage... the serious kind where no way he can make it 800 yards. More like DRT or close to it.
I'm thinking you anchored him through the muscle of the fore leg and into the brisket area for a low shot, then his movement snapped the arrow off for a non-vital hit... that most likely can do him in, just not within that area.
iSnipe