There were cops on ground floor. Does Joker have a secret super power - the power of escaping from towers? Because he did this in TDK as well and it also confused me there lol.
And how exactly was Joker not effected by the gas? Something to do with his earings, not breathing through his mouth? I didn't really get that.
The Joker's gadget-man gave him nose-filters that protected him from the gas. He likely shot out a window in an upper floor and escaped through that using his robot kids.
"You seem familiar with my name, but I don't remember smelling you before."
I assumed he got away while the Cops were all distracted with Batman. Remember Carrie said just after they got away that it was over, Joker was gone, and he killed a lot of people. So he must have done it during the big Batman vs the Cops fight.
shareWhile this doesn't apply to the movie, in the comic, he flies out by sitting on Bobbie (the boy robot).
And how exactly was Joker not effected by the gas?
Next time pay attention. Joker used air-filters to breathe.
When the snows fall and the white winds blow, the lone wolf dies but the pack survives.