Well, they are actively and knowingly hunting another human being. Simon's death could be considered accidental or manslaughter, but it wasn't planned. Piggy's death shows the reader that Roger is a psychopath. He doesn't even see Ralph and Piggy as humans (just hair and a bag of fat). Jack and Roger plan to hunt Ralph, and they know how they are going to do it. Plus they are going to put Ralph's head on a stake (which suggests that they may cannibalize Ralph's body). Finally, the hunters set the island on fire in order to smoke Ralph out. This shows their madness because they are also destroying their own environment (killing the pigs and burning the fruit trees). Just like the madness of the nuclear war in the macrocosm, the boys' microcosm is also destroyed because of their hatred for their enemy. Hope it helps.
