Why does the narrator build up to the moment he kills the catthe black cat?

The narrator builds up to the moment he kills the black cat to create tension and suspense, emphasizing his psychological turmoil and descent into madness. This buildup allows readers to witness the transformation from a loving pet owner to a violent figure, highlighting the themes of guilt, addiction, and moral deterioration. By detailing the narrator's internal conflict, the author deepens the Horror of the act, making it more impactful and reflective of the narrator's disturbed state of mind.