Have you read "Enemy at the gates"? Kind of dry in some spots, but good history about the Battle for Stalingrad.
I'm not saying that everything in the book is 100% true, I have no idea, but, the final shot was very similar to the second to last scene, where the political officer stands up to get shot, but in the book he thinks Vasilli(sp?) shot the major. The major shoots political officer giving Vasilli an indication of the major under a metal sheet. Zeitsev then puts a bullet though the sheet into the major, battle over.
Also, the girlfriend in the movie did exist. She was a heck of a sniper also, but unlike in the movie. She was severely wounded when a "cow"(her words) that was on her team set off a booby trapped mine. Zeitsev, in real life, thought she was dead, went on with his life and other women, never to know that she survived. She supposably was horribly heartbroken and lived out her life alone. So goes the story....?