He is trying to convinced us that he is not mad. By killing the old man with the vaulter eye.
Every night for eight days he will watch the old man sleep. He was cautious when he went into the room.
One the eight night the he drop the lantern and the old man woke up.He stayed still for a whole hour and then as his and the old man eyes met he got angry and pulled the old man off the bed and suffocated the old man.
After he suffocated the old man he chopped up his body parts and put it in under the floor boards.
The neighbor heard a noise from the house so she called the police officers and they went to the house.
The officers ask a couple of questions to him. They stared to talk privately and he heard the heart beat of the old man and he felt guilty. So he confessed the the officers the he killed the old man.