From fear, the knife is used to butcher pigs, and Jack's group becomes the hierarchical hunters. Jack's position as leader of this unruly band is not enough for him, however, and until he and his knife attain sole power, neither will be content. An interesting, yet ominous portrayal of Jack's conflict between survival, violence, and the lust for power comes in a dialog between Ralph and Jack while on a foraging exploration and they find a well-worn path:

"Men?"

Jack shook his head.

"Animals" (26).

Jack of course, associating the path with savagery, Ralph with possible rescue and civilization. In fact, again and again the two paths of bestiality vs. civilization pull Jack away from the other boys, but also show the nature of divisiveness and conflict within all the boys.

All is not lost, though, the dualism in Jack is again shown in his inability to kill the pig caught in some thorns (Chapter 1). There is still rationality, still humanity, and still a concept of blood and pain. But very shortly thereafter, Jack's transformation occurs and "the frustration claimed him," while he was carrying a spear but could find no prey (49). This bloodlust consumes him to the point which he gives into "the compulsion to track down and kill what was swallowing him up" (51). Bloodlust so deep and pervasive than any moral nature is gone, and he cares for nothing escape the butchery of the pigs, and the resultant scent, color, and spray of the bloodletting.

Jack's character clearly represents a path towards evil, a path towards the darker side of humanity. Jack uses verbal skill, physical intimidation, and fear as techniques of power. He becomes, if you will, the opposite of what he was. He finds no real reason to hold onto his pervious inner checks and balances, lest they control is animal urges which, he seems to believe, are the only manner in which he can survive. Like many fascist leaders, however, Golding seems to remind us that ultimately, outwardly...

Planning to sacrifice him to the Lord of the Flies, Jack burns Ralph out of his hiding place. Ironically, the fire that Jack created to kill Ralph was the event that saved him from his death. This is because the fire has attracted a naval officer. The presence of an adult brings the boys back to reality, and the rules, which they so easily forgot without the presence of adult authority, are violently remembered. Jack is no longer a savage, but an ugly "little boy" again, no more than a frail example that grade-schoolers develop destructive habits and bad manners when unsupervised.
Jack's shift from English snobbery to primal savagery, from verbal trickery to fascist ruling is a prime example of what happens when our civil selves are masked and forgotten, and the evil nature inside of us comes out. Jack never meant for all of that to happen, he was just a jealous boy whose feelings were hurt when he wasn't chosen chief, and who wanted to have some fun. Because of Jack's already violent nature, the beast inside of him was easily able to slowly transform his psyche until all he truly cared about was killing and eating, the basic primal instincts implanted in all of us. Since Jack was "the first to go" in a way, he became a leader for the boys who were influenced later in the book by the beast. Jack never meant for the anarchy that he and the Lord of the flies created together to kill, but once it did, it's total consumption of the children seemed inevitable. The only thing that could stop Jack from leading the tribe and himself into self-destruction, was the soldier from the outside world, whose warship buried the beast in the boys, and brought it out in the last warriors of a world that lay in ruins.

Reference

Golding, W. Lord of the Flies. New York: Penguin Books, 1983.