In Chapter Four of The Lord of the Flies, there is a passage that reiterates what the above quote conveys,
Roger stooped, picked up a stone, aimed, and threw it at Henry--threw it to miss. The stone, that token of preposterous time, bounced five yard's to Henry's right and fell in the water. Roger gathered a handful of stones and began to throw them. Yet there was a space around Henry, perhaps six yeards in diameter, into which he dare not throw. Here, invisible yet strong, was the taboo of the old life. Round the squatting child was the protection of parents and school and policemen and the law. Roger's arm was conditioned by a civilization that knew nothing of him and was in ruins.
Because the sadistic Roger has only been isolated from the civilized world he knew for such a short time, he yet feels the restrictions of a civilized community formerly which has kept him from striking poor Henry. Roger has not yet felt free enough to be able to step outside the bounds of civilization.
Later, when Jack picks up the clay and smears it onto his face to mask his features from the pig, he shows his visage to Roger, who "understood and nodded gravely." Jack, "liberated from shame and self-consciousness"--those restrictions placed by society, lets out bloodthirsty screams and runs about. Thus, the "locks and chains" are taken off and anarchy comes in as the hunters, in their enthusiasm for playing at killing a pig, attack Simon and kill him.
Likewise, Roger, released from "the conditioning of a civilization in ruins," gives full vent to his sadistic nature. Given the opportunity, he pushes a granite boulder that crashes onto Piggy's head, splitting it and projecting the bleeding Piggy into the sea. With the release of the evil side of their inherent natures, Jack and Roger force the other boys to help them find Ralph and kill him.