Judging from the wound channel, I'm pretty sure this was the slug that killed him. Entered on the left side below and behind the shoulder, passed through the heart (heart was actually hanging in three pieces from the aorta) and was lodged between the hide and the rib cage on the right side, just below the shoulder.

What I was wondering about was the lack of separation between the wad and the slug. Somewhere between the muzzle and the deer, I expected the wad to separate from the slug.