I didn't understand the fourth game

[Event "ICC"]
[Site "Internet Chess Club"]
[Date "2009.12.03"]
[White "nhkatz"]
[Black "bajerk"]
[Result "1-0"]
[WhiteElo "1343"]
[BlackElo "1219"]
[ECO "C21"]
[Opening "Danish gambit"]
[TimeControl "120+6"]

1. e4 e5 2. d4 exd4 3. c3 dxc3 4. Bc4 Qf6 5. Nxc3 Bb4
6. Bd2 Nc6 7. Nf3 h6 8. Nd5 Qxb2 9. Nxc7+ Kd8 10. Nxa8 Bxd2+
11. Nxd2 Qxd2+ 12. Qxd2
1-0