What do you think happened at the end of "The Killing Joke"?

the comic ? well, not sure, he could have let him go, he could have escaped, i think the beauty of it, is that it ends this way

I always assumed he sent the Joker to Arkham. They just realized there’d be no end to their conflict as Batman would not, ultimately kill him. And, of course, Joker would escape prison soon enough.