I am not sure how one is hit in the back of the head while using a grinding wheel. Maybe he turned away and it happened. ???
http://www.ktvu.com/ap/ap/california/worker-at-berkeley-plant-hit-by-metal-dies/nLWgF/
Phil
http://www.ktvu.com/ap/ap/california/worker-at-berkeley-plant-hit-by-metal-dies/nLWgF/
Phil