I had been and am; but why will you say that I am mad?
During the day, the narrator was kind to the old man.
How did you sleep?
But at night the narrator snuck into the old man's room. Ever so carefully he would open his lantern to shine on the old man's vulture eye.
One night the eye was open and the narrator decided that it was the old man's time to go. Then the narrator killed the old man with his bed.
The narrator hides the old man's body in under the floorboards.
In the morning, the cops come and inspect the bedroom. The narrator invites them to sit in the bedroom. Then he starts what he think is the heartbeat. The narrator goes insane and confesses to killing the old man.