How does Montresor's response to Fortunato's screams add to the mood as the story reaches its highest point in "The Cask of Amontillado"?

Montresor responds by screaming even louder and longer
than Fortunato. His response only adds to the eerie and macabre atmosphere of the story.
As readers, we can imagine how the screams of the victim and the killer are echoing in
the catacombs where the bones of the dead are strewn about. Montresor's response is that
of an insane man, adding to the mood. Most of us would probably react to Fortunato's
screams with shock, but Montresor responds in kind to Fortunato's
screams.