Batman Arkham Asylum?

Oh it's supposed to do that... I was watching the AA lets play by xcalizorz and he was as confuzzled as you were. Once that happens just keep playing the game, its like the beginning where you bring joker in but its batman on the strecher instead. You get shot in the head and you're now playing as zombie batman, you'll get the game over screen but just continue, you then have to do the hardest possible scarecrow mission