“It’s more of a frozen moment than you normally see in archaeology,” said Helene Wilhelmson, a researcher who specializes in the study of bones at Sweden’s Lund University. “It’s like Pompeii: Something terrible happened, and everything just stopped.”

Five bodies already have been unearthed amid the ruins of one of the settlement’s houses on the island of Öland, just off the Swedish coast. In a news release, Lund University said more human bones have been identified in other parts of the fort, suggesting there may be scores or hundreds of bodies yet to be dug out.

“There are so many bodies, it must have been a very violent and well-organized raid,” Wilhelmson said.