I'm going to kill the old man because of his eye!
There was a caregiver that took care of an old man but he had a disease. He loved the man he took care of but soon decided to kill the man because of his eye. He was then found insane.
The caregiver comes up with the idea to kill the old man.
The caregiver went into the old man's room seven times at midnight before the night he killed him, looking for his eye to be open. He slowly opens the lantern until the light shone on the old man's eye.
I admit the deed! He's under the floorboards! It's the beating of his hideous heart!
The caregiver killed the old man on the eighth night at midnight, he threw the old man's bed on top of him and suffocated him as he died.
After killing the old man, the caregiver chopped his body into pieces in the bath tub. He then put the parts under the floorboards in an attempt to hide the evidence.
The police come to investigate and caregiver admits to killing the man not because he was guilty, but because he thought he heard the beating of the old man's heart, and it got louder and louder until he couldn't take it anymore, so he admitted.