Help wich Joker comic is this....?

Question

There was this one comic that the Joker bombed or gased a Kindergarden classroom.....Does anyone know what the comic is called?.........I dont remember if it was a graphic novel or comic......someone help!

Answer 1

They mentioned that he did that in an issue of Hitman, they never actually show him do it.

Answer 2

I don't think it actually happened in a comic book, but was referenced in a 1996 issue of the comic book "Hitman".