QUESTION- Your 3 Favorite Slasher Films with a Female Killer

Yes, Judge Wargrave was the murderer in ATTN. I was talking of the basic set-up, though: assorted people sent to an island, where they're murdered off one-by-one, and there's the twist that one of the "victims" faked his own death (as is done on a larger scale in April Fool's Day).