Early in the novel we can see that Jack is a rather bossy, conceited boy. He believes that he has a right to be the chief on the island because "I'm chapter chorister and head boy. I can sing C sharp" (p. 29). When he is not elected chief he predictably feels hurt and aggrieved. Ralph generously offers him leadership of the choir group which significantly Jack requests be called 'hunters'. He clearly pictures himself as a deputy leader who will hunt and provide food for the group with all the manliness that entails.
When Ralph announces an initial exploration of the island Jack is quick to reach for his weapon, "Jack snatched from behind him a sizeable sheath-knife and clouted it into a tree." (p. 32). At this time we see Jack as very fired up to prove himself to the other boys having failed to be elected chief. However, during the exploration he is unable to complete the fairly simple task of killing a trapped piglet. Whilst he insists that he was only looking for a point to stab the piglet before it scampered off, the narration informs us "They knew very well why he hadn't: because of the enormity of the knife descending and cutting into living flesh; because of the unbearable blood." (p. 41). At this point Jack is still a young and innocent boy with character foibles, not so surprisingly without the stomach to draw the blood of a living animal. However his loud exclamation that he will not fail next time combined with earlier displays of 'born to rule' arrogance combine to form some ominous signs in an environment where there is no adult guidance or hand of restraint.