One night, some 1,500 years ago, a band of marauders infiltrated a stone ring fort on the shore of Öland Island off the south-east coast of Sweden. The attackers stabbed or clubbed every man in the wealthy village of about 200 or 250 people, killing children, as well. The bodies were left to rot where they fell. The scene at Sandby Borg was so gruesome that, though the details have been lost to history, to this day island locals consider the old fort, now a green hill, cursed.

The outlines of this incredible story comes from a three-year-long excavation of archaeological finds from Sandby Borg. According to Nicholas St. Fleur at the New York Times​, the ancient site attracted attention in 2010, when archaeologists discovered a skeleton in the doorway of a house. They later discovered more bodies, 26 in all. They all bore signs of violent death, including sword, knife and club marks. “It dawned on us that this was actually a massacre,” Clara Alfsdotter, a graduate student at the Linnaeus University in Sweden and an archaeologist at the Bohusläns Museum, tells St. Fleur. “They were basically going from door to door killing everyone, from young children to older individuals.”

Among the dead was an old man who fell across a an open fire, which burned through his flesh to the bone. Inside his skull, archaeologists found sheeps’ teeth, which Maev Kennedy at The Guardian reports could be interpreted as an insult from the killers to shame the man, who may have been a chieftain. Another corpse is that of a teenage boy who tripped backwards over another body, likely from a killing blow. Researchers also found bones from a months-old baby, showing the extent of the massacre. In one house alone, Kennedy points out they discovered nine murder victims.

The attack appears to have been stealthy or sudden, as the remains of meals, including cooking pots and half a herring, were found sitting by cooking fires. None of the skeletons exhibit facial or defensive wounds, which also indicate they were surprised and did not have time to fight off their attackers. Interestingly, however, archaeologists have not found any remains of women or girls among the dead. The massacre is detailed in the journal Antiquity.

So what, exactly, was going on at the Sandby Borg? St. Fleur reports that though the fort was located on the coast, it is unlikely that the attack came from the sea, since the high stone walls that surrounding it would have deterred pirates. The fact that whoever conducted the massacre left behind all the livestock, jewelry, coinage and other valuables, also offers persuasive evidence that it was probably not a raid by bandits. Because all the weapons in town appear to have been confiscated, the massacre could have been politically motivated.

The BBC reports that the period when the massacre took place was "during a turbulent period of intense migration." The Western Roman Empire which had brought stability and trade to Europe for hundreds of years had collapsed. The Huns were attacking from the east. Local tribes were fighting each other and within themselves as new power structures were established. A similar power struggle may have occurred on Öland Island itself, which was home to at least 15 ring forts.

Ludvig Papmehl-Dufay, co-author of the paper and an archaeologist at the Kalmar County Museum, tells St. Fleur that it’s possible someone at Sandby was allied with another village or political rival, and may have opened the doors through the 13-foot stone walls for the attackers during the night. “I think the purpose was to show some other people what happens if you mess with this group,” Papmehl-Dufay says. “This was more of a terrorist attack in that sense, the use of massacre as a political tool.”

We may eventually get more details about who perpetrated the massacre and why. The BBC reports archeologists have only excavated three out of 53 houses at the site and hope to uncover more if they can secure the funding for it.