EE1 put bolt-inner bearing housing. EE2 loosened outer fastener;bearing house pulled out.EE1 said stop;EE2 re-tightened fastener. Bolt in-place for alignment of shaft/flange. Vibration/movement from impact wrench may have let shaft spin on bearing. Pendulum effect occurred;paddles contacted EE1. EE exited tub w/o help; walked 300' to truck. EE1 stated legs hurt;driven to hospital.