lord of the flies

I don't think that the boys consciously wanted Simon and Piggy dead. Piggy was a great source of derision and humiliation. The boys enjoyed getting Piggy riled up and then making fun of him. It is Roger in particular that is a sociopath. Piggy's speech near the end of the book drives the boys to jeering and it is Roger that launches the boulder. I'm not sure that Roger cared if Piggy was dead or nor, he just wanted to hurt somebody. The boys were generally perplexed about Simon. They certainly did not want him dead. They just got lost in the hysteria of the storm and perceived him as the beast. By then the time any boys realized it was Simon, they were so hysterical that it did not seem to matter that they were killing Simon or any other boy for that matter.