IIRC, the inspiration for Fritz Lang’s “M”

Following Haarmann's arrest, rumours circulated that Haarmann ate the flesh of his victims, or sold it on the black market as pork or horse meat.[34] Although no evidence was ever produced to confirm these theories, Haarmann was known to be an active trader in contraband meat,[35] which was invariably boneless, diced, and often sold as ground meat.[36] When asked where he obtained the meat, Haarmann sometimes said he had obtained the produce from a butcher named "Karl", although investigators would later note that the stories Haarmann told his acquaintances regarding the origins of this individual varied.[37][38]

😶

Haarmann became known as [...] the Wolf Man (Wolfsmensch) because of his preferred murder method of biting into or through his victims' throats

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There's a great German movie with Götz George in a menacing performance: https://www.imdb.com/title/tt0114704