The sad thing is that mass shooters study, emulate, and inspire each other. The more info that is out there about each particular one... well, more for the next one to use in their planning.
That's a good point. I actually just read about that in the book "The Gift of Fear" by Gavin De Becker ---which I highly recommend, BTW. The author is an expert at recognizing pre-violent behaviors and owns a security firm that protects high profile and high risk families and government officials.
Something else I read in the book & found interesting...
A person who sees no other alternatives but violence will likely become violent in the immediate future; it's one of the strongest pre-violent indicators that exists. He wrote... "A person who feels there are no alternatives will fight even when violence is not justified, even when the consequences are perceived as unfavorable, and even when the ability to prevail is low."
JH made a list of "alternatives to death" in his notebook, and under his list... he wrote, "Despite knowing death is false and a suboptimal response, I couldn't find a working alternative."
The author actually talked about several things I think are true of JH... in my personal opinion, of course.
Here's a few of them...
People never, ever "just snap". There's a process as observable as bringing water to a boil.
Many violent criminals have self-defeating personalities. It's as if he expects people to slight or harm him. This causes him to alienate himself, which causes others to treat him as he expects them to.
For mass murderers, it's not the target, destination, or journey that matters... it is the act itself.
Mass murderers don't fear going to jail, they fear they're going to fail and that is unacceptable to them. Every cell of the MMs being shouts extreme narcissism. He is too self-absorbing and relentless to fail and is expressed at the heart of him... a desire to stand out and be in control.
He wants what everyone wants: recognition and significance. Individuals who don't get that feeling as a child seek ways to get it as an adult. It's as if they've been malnourished for a lifetime and seek to fix it with one huge meal.
*(I found this to be extremely significant when JH mentioned the reasoning behind his "parasuicide" in his psych interview. He said he did it because he didn't feel like he was being listened to and felt like his opinion didn't matter about his family's decision to move to San Diego... he mentioned not wanting to leave his friends and make new ones.)
Behaviors common to all mass murders:
They display some form of mental illness
They research their target
They create a diary, journal, or record
They obtain weapons
They display an exaggerated sense of self (grandiosity or narcissism)
They identify with a past villain or assassin
They have the ability to circumvent security
*(JH was able to do this--in his mind--by creating a diversion at his apartment prior to the shooting.)
The entire book was very informative and insightful.