Fiction!
That duel never happend.
Here is what Anthony Beevor (author of Stalingrad) had to say:
"Indeed, the whole story of the sniper duel is fiction. There is absolutely no trace in the German military archives or SS records of SS officer Heinz Thorwald. Also there is absolutely no report of the duel in the Red Army files which concentrated on sniper activities (the daily reports of the Political Department of Stalingrad Front to Moscow) This great story can be classified as Sovjet propaganda."
The quote below is from a BBC News article:
"Mr Beevor, whose acclaimed tome Stalingrad is rapidly becoming the definitive text on the battle, said while Zaitsev was a real figure there was no evidence to support the existence of Koenig.
He said: 'I've been through the Soviet Ministry of Defence's archive in Podolsk and there is no record of such a duel.'
'If it had taken place the Soviet propaganda machine would have leapt on it.'"
For info on the German troops visit
http://www.skalman.nu/third-reich/ and for info on the Soviet troops visit
http://www.skalman.nu/soviet/
/Marcus