Russian officers did really shoot their men if they retreated or fell back. In some of the Call of Duty shooting games it shows this. If the men were to run away from a German MG gun that was mowing down dozens of their comrades their officers would be waiting behind and would shoot them on the spot. It was suicide to be in a position like that. Many of the German soldiers who witnessed this happening even felt sorry for the Russians who were shot for being "cowards" and "traitors" just for falling back to try to save themselves.
Zeppelin, here's a great website on the battle of Stalingrad. It has a lot of photos. Link:
Stalingrad battlefield information
Stalingrad is probably one of the most famous battles of WW2. Lots of books and movies have been made about the pivotal battle. Thousands of soldiers along with civilians died there. There's a famous book about Stalingrad called, "Enemy At The Gates" which, tells the history of the battle.