Vasily Zietsev did it first...
I didn't know that. they were both some of the best snipers in history.
Zietsev nailed the chief of the German Army's sniper school, Maj. Heitz Thorvald during a multi-day counter-counter-sniper duel in Stalingrad IIRC. The scope of Thorvald's rifle is still on display in a museum in Moscow.
The duel was (over)dramatised in the movie
Enemy at the Gates, even if they got Thorvald's name wrong....
If you're a sniping fan, check out
http://www.snipercentral.com/ Has a great writeup on Carlos