Mental Health is absolutely one of them. General parenting is another. The sensationalism and "villian" worship of sorts that occurs with these things is another. Yes, gun / weapon regulations are part of that as well. So is discussions regarding our culture. I have the whole "video games help cause this" type of arguments, but I still see and understand merit in the notion of discussions regarding violence in our culture even if I don't agree with those necessarily saying it's definitely a problem or needs to change.
There are a whole hosts of legitimate avenues to discuss.
But NONE of them are ever going to get worked out in the first hour after something like this happens, and none of them are going to actually cause any realistic, useful, honest, worth while debate or discussion to happen in that first hour either. If anything, the constant need to push a political agenda (and spare me LMR if you somehow are deluding yourself into thinking that part of his "mimicry" wasn't pushing a political agenda that weapon regulation doesn't work) IMMEDIETELY in the wake of these things just harms the chance for anything meaningful to ever be discussed or come out of them.