Jack's transformation from proper English schoolboy to ruthless, savage killer is one of the most shocking in the Lord of the Flies. Like the naval officer at the end of the novel, the reader, too, is left wondering how come a group of nice, English boys could so quickly deteriorate into a wild pack of savages. The answer, of course, is Jack. His challenge of authority and own personal descent into violence sets an extremely negative example for some of the other, more impressionable boys.
The first moment in Jack's regression into a savage occurs the first time the boys experiment with making masks. Jack "looked in astonishment, no longer at himself but an awesome stranger" (63). The mask liberates Jack from his inhibitions, giving him the boldness to act, freeing him from "shame and self-consciousness" (64). Only moments later, Jack makes his first kill.
"There were lashings of blood," said Jack, laughing and shuddering, "you should have seen it!"
The thrill of the kill is upon Jack, making him feel powerful and respected for his ability in the tribe among the other boys. Jack has come to see violence as a tool, helping him to gain power in the tribe. This sentiment is never more evident than immediately after Piggy's death. Jack uses the horrifying moment to solidify his power over the other boys:
"Suddenly Jack bounded out from the tribe and began screaming wildly.
'See? See? That's what you'll get! I meant that! There isn't a tribe for you anymore! The conch is gone--'
He ran forward, stooping.
'I'm chief!' (181)
Any aspect or claim to civilization on the island died with Piggy and the destruction of the conch. By now, Jack has completely given himself over to savagery, first by demanding Ralph's exile and then later by planning his death. Ralph can only guess what fate awaits him at Jack's hands:
'What could they do? Beat him? So what? Kill him? A stick sharpened at both ends" (198).
The stick sharpened at both ends suggests that Jack means to kill Ralph and then mount his head on the stick, as he did the sow's head. Jack has truly become a savage; by planning to treat Ralph as the hunters did the sow, Jack has completely lost all value for human life.