On the evening of March 31, 1922, six people were killed at Hinterkaifeck, an isolated farmstead located between the Bavarian towns of Ingolstadt and Schrobenhausen. The victims were Andreas Gruber (63), his wife Cazilia (72), their widowed daughter Viktoria Gabriel (35), Viktoria's children Cazilia (7) and Josef (2), and Maria Baumgartner (44), the maid, who had arrived at the farm for the first time that day. Their bodies were not discovered until April 4, four days later.
The crime scene reconstruction suggests a methodical sequence. Four of the six victims—Andreas, Cazilia the elder, Viktoria, and young Cazilia—were lured or led individually to the barn, where each was killed with a mattock (a heavy agricultural tool similar to a pickaxe). The staggered nature of the killings indicates that each victim entered the barn without awareness of what had happened to the previous one. Seven-year-old Cazilia had torn clumps of her own hair out—evidence that she survived the initial blows and lay dying in the barn for some time. The maid and the infant were killed inside the house, apparently in their respective rooms.
The detail that elevates Hinterkaifeck from a grim rural murder to an enduring forensic puzzle is what happened after the killings. Someone remained at the farm for several days. The livestock were fed. Meals were prepared and consumed in the kitchen. Smoke was seen rising from the chimney. Neighbors noticed but thought nothing of it—the Gruber family was known to be reclusive. When the bodies were finally discovered, the farm was in order. The animals were healthy. The killer had, by all appearances, lived in the house alongside the corpses of the family for the better part of a week.
Andreas Gruber had told neighbors in the days before the murders that he had found unfamiliar footprints in the snow leading from the forest to the farm—but none leading back. He had also found an unfamiliar newspaper and heard footsteps in the attic. He did not report these observations to the police. This omission has fueled speculation that Gruber knew or suspected the intruder's identity and had reason not to involve the authorities.
The investigation, conducted by the Munich police with assistance from the Bavarian state detective bureau, identified over 100 suspects without making an arrest. The victims' skulls were removed and sent to clairvoyants in an attempt to identify the killer—a practice that reflected the investigative desperation of the era rather than any methodological soundness. The skulls were subsequently lost during the Second World War.
Theories have proliferated over the century since the murders. The most persistent centers on Andreas Gruber himself, who was rumored—and in some accounts, formally investigated—to have had an incestuous relationship with his daughter Viktoria. Young Josef's paternity was questioned. Some researchers have speculated that the killer was motivated by knowledge of this relationship, or that the motive was connected to Viktoria's late husband, who had died in the First World War under circumstances that were never fully clarified.
No arrest was ever made. The farmstead was demolished in 1923. Hinterkaifeck persists in the German criminal imagination as an irreducible mystery—a case in which the evidence is extensive, the horror is specific, and the answer remains absent.