Instances of the US coming across the camps are well documented but not so much by the Russians that I can find. Did the Russians do anything different? Did they behave appropriately? What happened to the prisoners immediately after discovery?
I probably can't give you the full picture, but one of the really important things they did was document it in writing. Vassily Grossman, for example, wrote the The Hell of Treblinka about his experience liberating a camp.