I had similar/same problem in this quest but it was on 5/6 (I did thread few days ago so you can read it, maybe it will help) and I just can suggest you to reboot your game, then go to the last spot where you shot him and find blood trail (or at least try, watch down to the floor and go to next location where he have to be). Then you will find him.
P.S. : for the future, complete line of trust quests with Jeremiah before you kill the bear, because you couldn't speak with him after. I stucked on it, so I wait for the patch