My take
Childhood trauma from my own experience and dealing with a psychologist, I have a disassociation with other humans. I have no problems with people dying. My psychologist would say it comes from a human you loved and them claiming they loved you treating you less than human. Other Humans doing nothing about it. Parents need to be taught best practices for raising kids, not just trial by error.
Personal Crisis from my perspective being taught I could over come anything and strong belief in myself plus experience with over coming crisis from early years prevented me from turning but led to a breaking point where I needed psychological help. People can be taught how to see signs of crisis in others and can be taught how to teach self belief better.
Script or Roadmap This is why the mass murders have increased. The internet, it is so easy today to find people who support your beliefs. You want to kill someone, you can find groups that will support and help you plan to do it. It the most scary thing about this study for how can you fix this. I grew up with enough experience that the internet can not influence me but I fear this next generation. People to People interaction gets less and less everyday.
Access to a firearm This is pretty much a Duh reaction. Of course they must have access to a firearm. To take away the right to own a firearm because an extremely small portion of the population may shoot people is not an answer. We should limit access to unnecessary deadly weapons but people should and do have the right to bear arms. I advocate for a similar approach as to driving. You must be licensed, registered and own insurance. Registration and Insurance would be dependent on the type and quantity of weapons you have. Licensing would require a written and hands on test. Safety and reasons for not shooting humans major part of test.
Driving is not a Constitutionally guaranteed right, it is a state granted privilege.
Therefore your entire premise fails. Licensing is an infringement on a right. Registering firearms serves one purpose, to create a confiscation list. It is no ones business what weapons I legally have. Reasons for not shooting humans would be part of your test ? How about simply knowing the law that says you may not use deadly force unless you believe your life, or someone elses is under immediate threat ? Simple, huh ?
The overwhelming majority of the shooters studied, had no legal right to own a firearm.
So, once again laws effecting the legal purchase of firearms is touted as a solution.
Yet the failure of laws prompts the shootings in the first place. These proposed laws will also fail. Murderers don't worry too much about breaking the law when obtaining a firearm to kill someone.
These crazed shooters are created by sociological and psychological pressures, apparently relative new ones, since up until the 1960's they didn't happen. They didn't happen when guns were much easier to obtain.
A firearm is an inanimate thing. The killing comes by the desire of the one firing it.
And there is the issue that must be addressed to stop this crazed killing, the person.