This story shows an obviously deranged man after having just killed someone and who is now trying to convince us (the readers), or perhaps even himself, that he is not crazy. The man claims that he is merely extraordinarily evolved in his senses. 
Of course we learn more with each sentence that this guy is anything but sane, no matter how much he likes to believe otherwise, and we see him reach his boiling point to eventually committing his crime and later fessing up to it. 
The question that lingers, however, is: was it guilt that made his crazy pop out again in the end or was it just that: crazy? Who knows.