Edgar Allan Poe- "The Tell-Tale Heart"

           "The Tell-Tale Heart" is another one of Edgar Allan Poe's odd, thrilling short stories. In this short story the narrator lives in a house with this extremely unattractive old man. Every single time the narrator looks at this old man, he cant take it because the man is so ugly and has this bulging eye that creeps him out. This eye makes the narrator so incredibly freaked out that he desperately wants to get rid of the old man. He finally decides he will get rid of the man by killing him. He tried many times while the man was asleep; however he could not bring himself to do it. But in the mornings when he sees the man with his eye open he wished he had killed him. Finally he sneaks into his room, kills him, cuts apart the body into pieces, and puts it under the wood floor. The police come because the neighbors reported a shriek. They inspect the house and find nothing, so they all sit in the very room in which the old man is buried. The narrator is haunted by the heart beat of the old man and finally goes mad, ripping the floor up, revealing the remains of the man.
          Again Poe has written another weird creepy short story that I have found very interesting and entertaining. This story shows guilt in an interesting way. The narrator did not go crazy because he was mad and rip up the floors revealing the man, however his guilt ate away at him so much that he could not take it any more.  Many people feel this way inside about guilt, and Poe shows what too much guilt will do to one; eating away at them. He uses the heartbeat of the man to represent the narrators guilty conscience.

Question: How did he know the 'old man'?