While it is a good thing that we are paying more attention to the problem of mental illness, we are never going to be able to understand, predict or prevent someone as mentally ill as the Vegas shooter from going off the deep end. Or at least we are far enough away from being able to you may as well say it is effectively never.
I get a kick out of the republicans who throw out there the same tired nonsense that it isn't about removing weapons like what were used in Vegas it's all about mental health care (as if they give a real fvck about health care anyway). It is naive to believe this person, who by all of the accounts we have heard from people allegedly close to him -- a brother, a girl friend -- never displayed real signs he was capable of such a murderous rampage could have been prevented from doing something horrific if he just had received the 2017 version of mental health care. We don't know enough about the human brain to understand what could make someone open fire on hundreds of strangers who were no threat to him and injure or kill hundreds. In 2017 the only way this massacre could have been prevented was if the means of killing so many people so quickly were unavailable. Period.
The truth is these things are going to keep happening. Over and over again. My guess is somewhere there is someone with the same level of mental illness who has been twisted into believing that there is some reason he (probably a he) needs to go on a rampage and kill dozens, or maybe hundreds of innocent people. In fact I'd be surprised if as much time passes before it happens again as happened between the Pulse Nightclub killings and what happened in Las Vegas. And whoever this person is, I bet there are people close to him who will express surprise and disbelief that he was capable of doing it.