Resignation after 13 Moves

In a game of speed chess, my opponent resigned after only 13 moves. He was Anotherperson99 of the USA, who played white. Here are the moves of the game along with my commentary:

1. d4 Nf6
2. Bf4 d6
3. Nf3 Bf5

White usually plays Nc3 before Nf3. This allows the move e4.

4. e3 Nc6
5. c3 e6

I have more development than white.

6. Nh4 Bg6
7. Nxg6 hxg6

I have doubled pawns, but I have opened the a-file for my rook.

8. Be2 Qd7
9. Nd2 Be7
10. Qb3 0-0-0
11. Bb5 a6
12. Be2 e5

I play e5 in the hope of creating a double attack.

13. dxe5 dxe5

Black's move is a blunder. He should play Bg5.

Now the bishop on f4 and the knight on d2 are under attack. White cannot save both pieces. Unable to avoid the loss of a piece, white decides to resign.