I don't want to speculate about who the killer is or isn't, but I think that the zombies are towns people that died in the events that Mr. Stewart recalled a couple episode ago. Though that doesn't explain Nightmare land or the hell hounds.
" Vinny saying in the zombie voice "Monet was so troubled."
When was this? "
When VJ were going through the Art House. It was after they had solved the tree puzzle, but before they fought the 2nd inviso-bitch. I'm pretty sure it was last week sometime. Maybe tuesday or thursday.