I'm not certain personally. The dialogue and the twin guns feel a lot like Jason, but I'm actually leaning towards the Joker. Morrison said that he had a new angle to explore the character and that he would return to the Joker soon enough, the Red Hood does directly connect with the Clown Prince of Crime, Professor Pyg's carnival had certain familiar elements and it just feels like the Joker. I can't explain that last part. Could be Jason, but I'm extremely doubtful it's anyone new.