This sounds like role play to me. This seems to be an individual who had taken on the identity of a villain in the Batman film, someone who wanted to get inside it and play a part.
It seems to be something to do with reality and fantasy, and not wanting to separate the two.
Some computer games allow you to get inside exciting events and experience feelings that you would never have in a normal life - killing people, stealing cars, racing cars, meeting strangers, taking risks, etc. They allow you to take on a different persona, change your appearance - in fact they provide hugely imaginative, exciting, deeply pleasurable experiences for millions of people.
People walk around living their daily lives with all this bubblling in their heads. But most peole manage to separate out what's real life from their fantasy life.
I wouldn't ban these games (it would never happen anyway) so a way to start protecting people is, I would have thought, to ban guns.