The Plot Hole I noticed in Batman Begins........

Historically Jack Napier (AKA The Joker) kills bruce waynes parents, then becomes the Joker and Bruce puts 2 and 2 together and they become rivals and such well in Batman Begins Jack Napier is shot and killed after his trial and then at the end of the movie they say theres a new evil that leaves behind Joker cards on his victims, now how can that happen if Jack Napier is dead??? also Batman is supposed to be the person who creates the Joker by accidentally pushing Jack into a tub of chemicals and this never happens so how can the Joker exist????? Does anyone else notice this?