How does the author use tone to create tension in pages 59-61?

In the section you've cited, the author leads up to the murder of Ikemefuna. These pages are filled with suspense and foreboding. Okonkwo, for the first time seems to be perplexed and indecisive, and as they hike farther into the bush the tone becomes more oppressive: thick with anticipation and apprehension. The tone of the final murder is both chilling and sad.