This is taken from a real game. the next moves were: 1...Rb6 2.Be4... and so black lost his opportunity to make checkmate in 4 moves. Try to solve the puzzle:

4...Qa2# works too, as does Qb4#

 had to figure out which one you picked.

Yes, i know there are few possibilities at the last move, but the most important are moves 1 and 2. 

Can you make puzzles out of your own games? i'll be glad to see them.

Does 1. Qa4 not get the job done the same way? 

Actually i now see that there is a problem with the puzlle, because of the next possibility: 1...Qa7 2.a4 Rxb2+ 3.Kxb2 Qxa4 4.c4 Qa3+ 5.Kc2 and eventually the king can escape. So your proposition Loomis( 1...Qa4) is the right one, as it prevents 2.a4...

But after 1 Qa7 2 a4 Qxa4 White still seems doomed to lose rather quickly.  Also after 2... Rxb2+ 3 Kxb2 Qxa4 4 c4 there is mate in two:  4... Qb4+ 5 Kc2 Ra2.

There is no mate in 4 in this position. White can continue Qxe5+, Re1+, etc.

ok, so the king can't escape in this possibility, thanks tonydal.

fleiman, if you add the moves 1.Qxe5+ Kxe5 2.Re1+ Kf6 3.Rxe6+ Kxe6 4. Bf7+ Kxf7 it will be mate in 8, but because i said as given that it's mate in 4, there is no problem.