A.) He can't bring himself to arrest his old friend. Twenty years before, the two friends decided that they would meet there at the restaurant whatever the conditions of their health or wealth. When Bob arrives at the restaurant, he finds that his best friend has turn into the most wanted man in 3 states. He still loves his friend, so he doesn't want to arrest him. Instead, he sends a plainclothes man to do the job. <span />
The narrator was guilty that he suffocated and dismembered the old man. When the police arrived and had a chat with him, the guilt got to him and he confessed his crimes.