Human rights advocates and lawyers have long pointed to al-Khafsa as a site of mass killings by the Islamic State. “Eyewitnesses told us they saw Islamic State fighters bringing groups of people by buses and executing them,” Attiyah said. “Many were beheaded on the spot.”Attiyah’s own relatives, an uncle and cousin who served in the police, were killed by the Islamic State. He said he hopes the excavation will finally lead to the identification and return of victims’ remains to their families. The Islamic State group once held territory spanning nearly half the size of the United Kingdom across Iraq and Syria.