Could Otzi simply have slipped and fell backward and stabbed his back with an arrow that was holstered pointing the wrong direction? The holder for the arrows could have been slung to low with an arrow that was positioned pointing up. Climbing upon a slippery iced over rock the arrow sling could have swung back, with him falling over backward onto the point. The high altitude locale where he was found could have contributed to faintness also.
Something is not right. This message is just to keep things from messing up down the road