His hands over his head [closed]
Imagine someone crouching on all fours (knees, feet and hands in contact with the ground), who is then so fearful that they bend lower at the front end, place their hands over their head and place their elbows and possibly also face on the ground. Or, if you would rather, imagine that the author has been a little careless and written something that only a skilled contortionist could feasibly attempt.