The Soviet POWs (and citizens) who returned to the Soviet Union were seen as traitors to the USSR. Stalin saw them this was because if you were captured, you did not follow Order no. 270, which stated that you were to die and not be captured. Stalin executed more than 100,000 Red Army soldiers, and arrested a few hundred thousand more. Over two million civilians were arrested for treason.

Source: http://gulaghistory.org/nps/downloads/gulag-curriculum.pdf

Great source if you are looking to get more information on the USSR's extensive prison system under Stalin, and how it was used to his benefit.

As for the Jews who were liberated, I know the Soviets first came upon a number of killing camps, where there were little to no Jews being housed there. Many of these camps resources had been destroyed due to the Germans trying to hide the camps' purpose. When they arrived in Auschwitz in 1945, there was only a few thousand prisoners still there, and again, much of the camp had been destroyed, but not enough to hide what had happened there. 60,000 prisoners marched away from Auschwitz in the final days of the war, as the Germans knew the Soviets were close and the war was soon to be over. There's accounts (source 2) that the Soviet soldiers helped the prisoners find food. Although you may think that the Soviets would have killed or taken these people prisoners themselves, they were fighting with the Allies and knew that they would not be able to get what they wanted out of the post-war talks and treaties. Many of their own soldiers were not arrested until arrival back in the USSR.

I could not find any personal primary accounts of the Soviet soldiers accounting what happened, but here is an interesting account of someone who was with the Soviet soldiers when entering a camp: http://www.eyewitnesstohistory.com/maidanek.htm

Sources: http://www.ushmm.org/wlc/en/article.php?ModuleId=10005131 http://alphahistory.com/holocaust/liberation-of-the-camps/

I hope that helps!