In "Lord of the Flies", what effect does the pig hunt, the kill, and its aftermath have on Jack and his hunters?

The situation with Jack and the hunters, in "Lord of The Flies," was already stressful at best, but after the hunt it became worse.  Once Jack actually killed a pig, and the hunters helped in this task, the "blood-lust" for another kill took over.  After this episode, civilized behavior continually regressed.  All Jack could think about was the hunt.  He didn't care about the fire, saftey, or rescue.  "Kill the pig, Kill the pig, Kill the pig."  This became their mantra. 

"The true chilling revelation, however, is the full emergence of Roger’s character. Previously a strange loner, his personality has emerged as truly sadistic. Even more so than Jack, Roger loves the hunt for the pain he can inflict. He slowly drives his spear into the anus of the sow, torturing it more than killing it. This is the brutal extension of his previous torture of Henry on the beach.

Another indication of the descent toward savagery the boys are experiencing comes through the hiding of their identities with paint. Jack especially is uninhibited when he is made-up; he brazenly steals the fire and dances naked in front of Ralph. His identity is truly transformed and made unrecognizable by the paint. "