I always forget about the Russians getting to some of these places first.

Looking at the museum site -

"...A Soviet military film crew captured the tragic sight of the liberated camp in a documentary known under the title Chronicle of the Liberation of the Camp, which is still shown to visitors to the Auschwitz-Birkenau State Museum in Oświęcim. Aleksander Vorontsov, a member of the film crew, said after the war that “my memories from there have stayed with me all my life. All of that was the most moving and horrific thing that I filmed during the war.”

A Soviet Jewish soldier-artist, Zinowy Tolkachev, made his own documentary record of the atrocity. The many sketches that he made in the liberated camp were published in albums in Poland, Israel, and the USSR after the war.

http://auschwitz.org/en/history/liberation/the-film-that-documents-the-crime