Three key events contribute to Simon's murder:
1. The storm that night terrifies the boys. Ralph almost succeeds in convincing the boys to return to the shelters for safety, but Jack intercedes by rallying them to do his hunting dance in a circle. The storm also contributes to the climate of fear felt by the boys, making them more suspicious and reactionary to Simon's later appearance that evening.
2. The dance is the single largest contributing factor to Simon's death. Participating in the mock hunt whips the boys into a blood-thirsty frenzy, enabling them to kill Simon brutally without logic or forethought.
3. Simon's decision to wander away from the other boys also leads to his murder. Then he shows up at the most inopportune time possible in an incapacitated state from fainting earlier, so he is unable to defend or protect himself.
Prior to Simon's murder, Jack has told the other boys, "I'm not going to play any longer," and has left Ralph's group. During the day he draws many boys after him, and, now "brilliantly happy," tells them he is going to be their chief. Jack leads the boys on a successful pig hunt.
In the meantime, Simon has sought out his private retreat, and while there falls into an epileptic seizure after having a vision of the Lord of the Flies. Jack's boys raid Ralph's camp and steal fire; Jack then begins cooking the pig on a large rock on the beach. All the boys except Piggy, Ralph, and Simon are attracted to the tantalizing meat, and Jack sets himself up as ruler, sitting there "like an idol." Ralph and Piggy eventually succumb to the temptation and joint Jack's feast.
In the forest, Simon has regained consciousness. He decides to put an end to the "beast" talk once and for all by seeing for himself what the other boys were so afraid of. He makes his way to the top of the mountain where the corpse of the paratrooper bobs on its tangled parachute. He finds out what it is, and after throwing up at the sight of the decaying body, untangles the lines of the parachute so it stops bobbing up and down. From his vantage high atop the mountain, he can see all the boys below on the beach. Thinking to himself, "The beast was harmless and horrible; and the news must reach the others as soon as possible," he starts the difficult trek down the mountain to bring them the good news.
At this point, a thunderstorm comes up. The boys on the beach start to get frightened, and Jack gets everyone to "do our dance." As the boys are all in a circle doing a mock pig fight, Simon comes crawling out of the forest. In the darkness, with the lightning flashing and the rain pouring, the frenzied boys imagine Simon is the beast. They all pile on him and tear him with their "teeth and claws."