Volunteers in the Ukrainian town of Bucha are using black plastic bags to gather hundreds of bodies, pile them like logs, and heave them into mass graves. Some were shot with their hands bound behind their back. Some showed the bruises, cuts and burns that testify to their tortured final hours. All of them were left behind by the Russian troops who retreated under pressure, but only after this last explosion of violence, aimed not only at the Ukrainian soldiers who beat them on the battlefield, but on the civilians unlucky enough to be left in their grip, unprotected. A report from Human Right…