The story is unlikely to be true, but there's a slim chance that it could be these German serial killers in Greece and the story's been muddled through the multiple layers of retelling it took to get to us (from the professor who experienced it, to the professor's student, to the student's brother, who told us). The timeline roughly matches up, and the lack of free press at the time could also explain a lack of evidence specifically about the professor's experience.