In “Operation Keelhaul” U.S. forces returned thousands of `liberated’ Soviet POWs to the Red Army. They were marched a few miles away and then machinegunned to death.
Some of the returned Soviet POWs were machine-gunned but others were not. In the recounting I read the soldiers were put on a train bound for a re-education camp/gulag. On the way the train stopped near a large quarry. The solders were ordered off and sent to the rim of the quarry. There were thousands and thousands of Cossack families in the quarry which was ringed by Russian troops with machine guns. The POWs were forced to watch as the Cossacks were machine-gunned.
The author was wracked with worry about witnessing the event. Not because he cared about civilians so much as whether or not it indicated they’d also be killed. They concluded it was intimidation which meant they would not be killed. So it was a joyous occasion for the POWs. Kinda shows how morality can be grossly distorted under a totalitarian system. The author spent several years in re-education until his release. He was barred from re-joining the army.
Many thousand Cossaks (and some families) were also killed by the Russian-communists “guards” when they were turned over by the Allies after WWII.