During Last Laugh the Joker was killed/murdered by the hands of a member of the bat family. Yep, it actually happened in the main canon though only for a brief period of time. Believing Tim's dead Dick starts to wail on Joker. Thinking the whole thing is rather funny Joker puts salt on the wound driving Dick over the edge.
Tim shows up but by then Jokers' "gone." Someone (likely Batman) gives Joker CPR and Dick feels bad for breaking the rules.
The first page is Another example of why I believe Joker always knew who they were. I don't know why so many people are mad about the implication in newer stories. It's nothing new.