Why did the policeman stay after the narrator answered their questions in The Tell-Tale Heart?

In Edgar Allan Poe's "The Tell-Tale Heart," the policeman stays after the narrator answers their questions because he is suspicious and wants to investigate further. The narrator, despite his attempts to appear calm and composed, is visibly anxious and guilty, which raises the officer's suspicion. Additionally, the sound of the beating heart, which grows louder in the narrator's mind, ultimately drives him to confess to the crime, revealing the tension between his outward demeanor and inner turmoil.