Today, Ukrainian authorities exhumed a mass grave in Sloviansk, in eastern Ukraine. By the time I left the site, they had discovered eight decomposed bodies and they were still searching for more. From April until July 5, the city, now back under Ukrainian government control, had been under the control of anti-government insurgents.

Two neighbors who usually walk their dogs on the lawn next to the burial site told me that on the morning of June 11 an excavator arrived and dug a hole. Later, they said, they saw two men in camouflage drive a truck to the newly dug hole and dump in bodies wrapped in cellophane. The women said the truck returned to dump more bodies an hour later, perhaps 15 altogether.

It’s too soon to say whether the people buried there were victims of a crime. Several local residents believed the bodies came from the nearby morgue. At the time the bodies were allegedly dumped, there was no electricity in parts of Sloviansk, which would have caused a problem for refrigeration facilities used to store bodies in the morgue. When the women asked the insurgents who was being buried, the insurgents said they were unidentified bodies.

According to the two neighbors, later that evening the insurgents brought two priests to the grave, who seemed to be saying a prayer over the burial site.

Among the police, forensic experts, and journalists standing around the grave witnessing the exhumation, there were several local residents searching for loved ones who went missing when insurgent forces controlled Sloviansk. One woman said that insurgent forces had abducted her husband in May. She said that he called her on May 21 to say goodbye. He said that the insurgents were holding him and they would execute him in 15 minutes. The next day she identified his body in the morgue, but the insurgents refused to give her the body for burial. Another person standing around the burial site, a man in his thirties, said that he was looking for his friend who got into a fight on the street and was then picked up by the insurgents. Nobody has seen him since.

It’s understandable why these local residents wonder if the grave contains victims who died at the hands of insurgents. Insurgents systematically kidnapped, abducted, beat, and sometimes tortured activists and residents they suspected of supporting the Ukrainian government. Human Rights Watch, among others documented this pattern in Sloviansk and in other cities. We also documented the killing of a local politician whose body turned up in Sloviansk two days after he had been last seen in the custody of armed insurgents. Documents discovered by foreign journalists also indicated that insurgents carried out summary trials and executions in Sloviansk.

Only a proper investigation can help to determine who the people are whose bodies were dug out from the mass grave today, and what happened to them. Independently, it is crucial to bring to light the abuses that happened in Sloviansk while it was under insurgent control.