BUCHA, Ukraine (Reuters) – Forensic investigators began exhuming a mass grave in the Ukrainian town of Bucha on Friday, wrapping in black plastic and laying out the bodies of civilians who officials say were killed during a Russian invasion. Ruslan Kravchenko from the prosecutor’s office in Bucha said they had exhumed 20 bodies, 18 of whom had firearms and shrapnel wounds. He said two women had been identified, one of whom had worked at a supermarket in the town centre. “There are witnesses who can confirm that these people were killed by the Russian forces. Without any reason, they were just …