How does Fresleven's fate function as a foreshadowing of what Marlow will encounter later on?

"Fresleven — that was the fellow's name, a Dane — thought himself wronged somehow in the bargain, so he went ashore and started to hammer the chief of the village with a stick." Eventually the Chief's son stabbed Fresleven through the shoulder blades and killed him. Marlow will see plenty of brutality inflicted on the natives. Also the things that go on in the heat of the jungle stay in the jungle!