What brings the police officer to the house in "The Tell-Tale Heart"?

In "The Tell-Tale Heart," the unreliable narrator is vexed by the old man's eye, so he resolves to kill him one night while he is sleeping.  When the narrator goes into the old man's room to murder him, the old man lets out a scream, which one of the neighbors hears.  Since it is the middle of the night, the neighbor gets nervous and calls the police.  So, the police officers arrive at the house to inspect the scene and interview the narrator.  By this time of course, the narrator has buried the old man's body under the floorboards, and when the police come into the house, they suspect nothing.  The narrator's own madness and guilt lead him to reveal the body under the floor.  The police only arrived at the house on a neighbor's suspicion, but they end up bearing witness to the aftermath of murder.