Before I watched the movie "The killing joke" I read the comic again. I was always wondering why the gun of the joker has two barrels. Can it be possible that the main barrel is just used to trigger the flag with the words "click click click" on it?
The second barrel could be the "real" one that actually shoots bullets.
This theory could mean, that the joker had the opportunity to kill batman, but he decided to let the game go and just released the flag.
Has anybody ever thought about this? Here is a picture of that special gun.