'Black mass mastermind' behind Monster of Florence murders

Over nearly two decades a serial murderer branded the "Monster of Florence" shot eight courting couples in the Tuscan countryside, invariably at full moon, and sexually mutilated their bodies.

Here is Crime Library's entry on the case.

Novelist Douglas Preston has written an as-yet-to-be-published-unless-you're-a-subscriber piece on the case for the Atlantic but here is an interview about his experience.