The cautious man decided that discretion is the better part of valor and quickly alerted the authorities.
According to the Morgenposten newspaper, police officers quickly arrived at the scene and after a swift search of the premises the offenders who were making these spooky noises were finally discovered. They were a pair of mating hedgehogs.
"Hedgehogs hiss loudly during a mating ceremony that lasts for about an hour, with male producing most of the noises," an expert from the veterinary faculty of the Ludwig Maximilian University of Munich explained.
Started by police officers' flashlights, the amorous mammals fled, leaving the cautious homeowner in peace.