It has been customary in battles since the beginning of time that when a soldier has been mortally wounded that if he has not died yet, to risk from being captured, he will ask a fellow soldier to take his life so he does not do it himself. This practice is to prevent the taking of prisoners. The Old Testament is filled with examples of this, including in Judges where King Saul was faced with that very circumstance. And in the New Testament, Jesus cried out for the ultimate coup de grace to the Father.