Either he had to leave the computer quickly, or he saw no way out of the mate threat at f7, considering his rating.
Odd Resignation

Either he had to leave the computer quickly, or he saw no way out of the mate threat at f7, considering his rating.
This was in an online chess game, and his rating is now 1252.

Well, I don't know if you guys noticed, but white is the side that resigned. A way out of mate at f7 has nothing to do with this.
To the OP:
You know how the knight moves, right? So, you can see how the Queen just moved onto a square where the knight can capture it. If you have any further questions, feel free to post.

Seems like he shouldn't have though :)
Good call.
This is one reason why a lot of chess coaches tell beginners to play to checkmate.

Yes, I did see that I could take his queen, but it still seems too early to resign. And yes, I probably would have made " an equally good counter blunder" :)

whats worse, giving your queen away for free or failing to see it?
Failing to see the hanging Queen is worse.
When you hang your Queen, it is because you can not see one half move ahead. When you don't see the hanging Queen, you are failing to see the very position right in front of your eyes.

Yeah, the queen is hanging but when I do something of that nature, I let my opponent move before I resign. I can't tell you how many times I have dodged a bullet because my opponent overlooked a hanging piece or something. I think before he resigned he should have made you move.
By the way, Wanderlei Silva is awesome.
Can you see any obvious reason this person would resign here?