Der Freischütz

When a hunter received a gun with the bullets that will puncture anything he pleased from the Devil, the Devil proposed a childish contract: the last bullet would puncture the heart of his most beloved. The moment the hunter heard that, he sought down and shot all the people he loved. Telling the Devil, "This magical bullet can truly hit anyone just like you say." The final bullet (the 7th) then punctured his own heart. He traveled to numerous worlds, doing whatever he felt based on impulse. One day, the marksman realized the Devil no longer followed him. He pondered why, then realized that his soul had already fallen to Hell. The contract had been fulfilled, so the Devil had left. The marksman, now a devil himself, continues to pull the trigger to gather the souls of others.