During excavations of the Iron Age ringfort of Sandby borg (ad 400–550), the remains of twenty-six unburied bodies were encountered inside and outside the buildings. The skeletons and the archaeological record indicate that after the individuals had died the ringfort was deserted. An osteological investigation and trauma analysis were conducted according to standard anthropological protocols. The osteological analysis identified only men, but individuals of all ages were represented. Eight individuals (31 per cent) showed evidence of perimortem trauma that was sharp, blunt, and penetrating, consistent with interpersonal violence. The location of the bodies and the trauma pattern appear to indicate a massacre rather than a battle. The ‘efficient trauma’ distribution (i.e. minimal but effective violence), the fact that the bodies were not manipulated, combined with the archaeological context, suggest that the perpetrators were numerous and that the assault was carried out effectively. The contemporary sociopolitical situation was seemingly turbulent and the suggested motive behind the massacre was to gain power and control.