The Tell-Tale Heart (1843) is a short story by American writer Edgar Allan Poe.
How Does The Narrator Kill The Old Man? The narrator kills the old man by smothering him under his own bed. He then chops up the dead body and hides it under the floorboards.
Why Does The Narrator Kill The Old Man? The narrator justifies his crime by saying that he couldn't bear to look at the old man's clouded, blind "vulture-eye".
I think we're supposed to assume that the narrator has some kind of mental illness - as, despite trying to convince the reader otherwise, he doesn't really have a good reason for killing the old man.