In "The Tell-Tale Heart, why does the narrator kill the old man?

the narrator killed the old man simply because of his eye which reminded the narrator of a vulture.

"Whenever it fell upon me, my blood ran cold; and so by degrees-very gradually-i made up my mind to take the life of the old man, and thus rid myself of the ye for ever." (Quote)

he also had stated that he did not have anything against the old man.

"I loved the old man. He had never wronged me. He had never given me insult."