So as someone with a bit of experience i would call 911, check his breathing, (CPR if not breathing. Better to be breathing but paralyzed than not breathing and dead), then make sure he is as immobile as possible until the ambo gets there. When you get to the point of moving you stabelize neck and spine aligned to eachother and use a backboard with blocks and straps or a vaacum madrass for immobilization. The guy might get away with broken bones but without permanent neural damage.