Straight forward 3 mover
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2. Rxf2 Qxg3+ 3. Kf1 Qxf2#
2...Qxg3+ 3.Qg2 Qxg2#
Also rxf2 rxf2 ! These are just taken from games to provoke thought and show that even in high level chess mistakes happen. This was the line that was played.
8by8, if you look at my post in this thread you'll see why 2. Rxf2 doesn't help white. (Somehow I knew someone would suggest this as a way to escape, yet even posting the line that refutes it doesn't help.)
1.Rxf2-Rxf2 2.Qxf3-Rg2! pinning the queen to the king.....
8by8, Rg2 isn't a legal move in that position because the king is still on g2.
Three moves to mate! Loek van Wely-Judit Polgar, 1997.