Jack and his choir were hunting a pig.
Jack and his choir were at the top of the mountain when Ralph spotted the smoke from the ship. They were supposed to be tending the fire, which they let go out while they were hunting.
When Jack and his choir first marched down the beach they stopped close to the platform and Jack, alone, vaulted onto the platform to speak to Ralph. When Ralph explained that they were having a meeting and said, "Come and join in." The choir began to scatter from close line. Jack shouted, "Choir! Stand still!" The choir obeyed.
Ralph allows Jack to be in charge of the choir because they are all part of the same group of British schoolboys, and he wants to maintain order and organization within the group. Jack's experience as head chorister in school may have also influenced Ralph's decision to assign him a leadership role.
Ralph takes Simon and Jack along with him on the expedition.
Jack and his choir became hunters and helped Ralph and the others hunt for food on the island. However, they eventually broke away from Ralph's leadership and formed their own tribe, leading to a violent power struggle.
When Ralph is elected to be chief he knows Jack is dissapointed (as Jack also wished to be chief) so he appoints Jack as leader of the choir and asks him what he wants them to be, to which Jack replies, "hunters."
Fleeing from Jack and his hunters Ralph stumbled onto the beach, near the shelters, and was confronted by a naval officer. Jack and his hunters also emerged from the jungle a short distance behind Ralph but immediately stopped their pursuit of Ralph on sighting the officer. The arrival of the officer saved Ralph from Jack and his hunters. However the officer was only there because his ship had sighted the smoke coming from the island. The smoke came from the out of control fire which Jack had lit to try and drive Ralph from his hiding place. In a typical example of irony by Golding the fire which Jack lit in an effort to kill Ralph proved to be Ralph's salvation.
He puts Jack in charge of the choir and asks Jack what he wishes them to be, to which Jack replies "Hunters."
When the boys elect Ralph as leader, in favour of Jack, Ralph puts Jack in charge of the choir and asks him what he would like them to be. Jack replies, "Hunters."
When Ralph is initially elected leader he confirms that the choir still belongs to Jack. Jack says that he wants his choir to be hunters, to supply the boys with meat by hunting pigs. After they light a signal fire on the mountain Jack says that his hunters will take on the responsibility for keeping the fire lit.
After Ralph won the election to be chief, leaving jack as the losing candidate, Ralph placed Jack in charge of the choir and allowed Jack to choose what he wished them to be. Jack chose, "Hunters."
Ralph told him he could be the leader of the choir boys and then he made his own group of only himself until people from Ralph's side went to Jack's side. :)
Jack is the leader of the choir and the one who leads the break away group, who split from Ralph's lot to form a tribe.