Zack Snyder proved pretty early in Batman v Superman that he wasn't afraid of making bold moves with beloved comic book characters by murdering Jimmy Olsen without giving him so much as a backstory. Naturally fans were a little pissed.
Notoriously, he also killed Robin as part of Batman's tragic backstory and had his suit preserved as a monument to his own failings in the Batcave. Despite the set-up of the Joker being the killer and the apparent suggestion that we might be heading to a Jason Todd/Red Hood sort of storyline, the murder didn't lead anywhere at all.
Instead, it was just there to remind Batman to be sad and that the Joker was a bad dude before he appeared in Suicide Squad and literally didn't mention it either. So much for that exciting Red Hood movie.
But now Zack Snyder has confirmed that it wasn't even Jason Todd who had been killed. He announced on his Vevo that it was actually original Robin Dick Grayson who was the fallen comrade, when responding to a comment about a Suicide Squad deleted scene...
So, basically, in the DCEU, there's no Robin, no Red Hood, no Jason Todd and no Nightwing. No wonder Batman was so lonely. That does make it somewhat odd that Warner Bros were pressing ahead with a Nightwing movie, though. Maybe they weren't going to let Snyder have Grayson's death as canon at all?