What's the significance of the empty Robin suit in Dark Knight Returns, and is it linked to A Death in the Family?

In The Dark Knight Returns, several panels show an empty Robin suit on display in the Batcave. I had always assumed this was a reference to the storyline A Death in the Family.

However I just discovered that DKR was written three years before Death in the Family.

So, what's the link between these stories? Was Death in the Family written specifically to fill in the background behind that empty suit? Or does DKR refer to an earlier story in which one of the Robins met with an unfortunate fate?