[officialtony]

I'm not sure you'll find anything in the book to cover that one. I think I would follow the process as it unfolds. I immediately call the strike and tell the batter who got drilled to step back into the box. I would not let him benefit from his illegal action. To send him to 1st base lets him benefit from stepping out of the box illegally in the first place and I don't believe any player should get that advantage. I think the intent of most FED rules backs that theory. His coach may argue that he couldn't avoid being hit, to which I might respond that if he had been in the batters box, the ball would have been behind him - AND called a ball.