One night, the Red Hood and his gang tried to rob Ace Chemicals. Batman intervened, and in the confusion the Red Hood fell into a chemical tank. His appearance permanently altered, and also in grief and anger over the death of his wife and unborn child, the Red Hood was no more, he was driven insane. The Red Hood was no more, and a new villain arose to terrorize Gotham - the Joker. Here we see versions by Si-MOCs, Lucas and R.K.Blast.
R.K.Blast also gives the variation of the story in keeping with the 1989 Tim Burton movie: