Maybe it was Jason (as Red Hood) who sent the newspaper with the message "you let your family die". Joker obviously sent the Robin suit with the message "Ha Ha, the joke is on you Batman". I have a feeling that we are supposed to think it was The Joker who sent both the newspaper and the Robin suit and to not suspect that the messages were sent by different people (especially non-comic fans who will not suspect the Robin that Joker "killed" to come back as Red Hood). Perhaps the fact that both messages have a different colour of writing is a hint that the messages were sent by different people (or maybe the Joker just didn't want to write the message on the newspaper in green, idk I am just guessing).
It makes sense to me though, that Jason (as Red Hood) sent the message on the newspaper (which is a more personal message) because Jason knows Batman is Bruce whereas Joker generally does not. Also, for what it is worth (probably not much and is just me reading too much into nothing) but the colour green, which was the colour of the writing on the Robin suit, could perhaps be representative of Joker (his hair obviously and along with purple and white are the colours that are mainly associated with The Joker, or at least they are to me) and red, the colour of the writing on the newspaper, could be representative of Jason as the Red Hood.
