In Lord of the Flies, each death or near death on the island reflects the gradual descent of the boys into savagery. Based on the previously stated...

You could argue that each death or "near death" act of violence symbolizes a different aspect of the boys' descent into savagery. Simon is the peaceful and insightful boy on the island. At the end of Chapter 8, Simon imagines the Lord of the Flies (pig's head on a stick) talking to him. The Lord of the Flies tells him that he (the Beast) is a part of the boys. In Chapter 9, Simon goes to tell the others that there is no beast, that the only thing to fear is the potential beast in all of them. Simon's wisdom is never heard because they kill him in a savage frenzy. It seems that they don't even recognize him on the beach. They literally and symbolically fail to recognize the voice of reason and wisdom. With Simon's death, the model of peace and wisdom is lost. 

With Piggy's death, there is a symbolic loss of order, intelligence, and reason. Piggy and the conch are tragically but fittingly destroyed together. The conch was the symbol of order, the one object that brought the boys together. Piggy was the intellect on the island and the only one other than Ralph to insist upon keeping the fire going. This is their best hope for being rescued, their best link to the civilized world. When he and the conch are destroyed, order is just about completely lost. 

In the last chapter, Ralph is being chased by Jack and his tribe. Near the end of the chapter, Golding stops using their names (with the exception of Ralph's name). Ralph is being followed by "a savage." The violent pursuit of Ralph is marked by a loss of the other boys' English (civilized) names. Now, they are simply savages. Each act of violence (Simon's death, Piggy's death, the shattered conch, and hunting Ralph) shows a different aspect of their descent. By the end of the final chapter, the boys have completed the progression from civilized to savage.