How did Jack free himself from shame and guilt that came from his need to hunt and kill?

Jack painted his face. The mask freed him from the old world and its rules.

He knelt, holding the shell of water […]. He looked in astonishment, no longer at himself but at an awesome stranger. He spilt the water and leapt to his feet, laughing excitedly. Beside the pool his sinewy body held up a mask that drew their eyes and appalled them.