when they were down , entragian had stopped , backed up , backed slowly over them ( there had been no wind then , audrey told them , and she had heard the sound of their bones snapping very clearly ) , got out , walked over to them , knelt between them , put a bullet in the back of the girl 's head , then took off the escolla boy 's hat , which had stayed on through everything , and put a bullet in the back of his head .