Tagging mass murderers with “mental illness” is wrong. It precludes both medical and social sciences. It is devoid of research of the science of psychology and causal studies and remedies. It is unsympathetic, prejudicial, and unusable.
Police investigations of the evidentiary facts have shown that individuals who commit such heinous crimes have spent time planning and even publishing their intent. They have harvested many poisons which have taken root in their minds — lies fabricated to seduce and compel a person to hold to some conspiracy theory mutated into delusions of the actual — a reality of an enemy that must be defeated — a dragon that must be slain. This is not the comedy of Don Quixote tilting at windmills. For pragmatic solutions, arming teachers has been suggested to thwart such catastrophes, but arming teachers would only make them a primary target in the minds of any armed intruder.
One may claim that this is a dissociative identity disorder, but please allow my experienced opinion: Lies comprise the building materials for the construction of a person’s thought processes and mindset. When the lies seem possibly true, and when melding them together seems like it could be a true scenario, and observing the world as in desperate need of action, then a call for heroism causes some to see a need to step up, to toe the line to, design a solution.
Evil. The thoughts which are not your own thoughts. One hasn’t studied the ideas in school or at the Library. One has been thinking about other things — like work or play or where they would like to travel, sights they would like to see, trying something new like fishing, surfing, go kart racing… whatever. Then some foreign thought pops into mind. It’s not yours. But it is so subtle, it appears harmless, and so it is not rejected. Later another thought. Without analyzing the construct or wondering “Where did that come from?” it seems to have become your own. But it is not yours at all.
Religions have explanations for this evil, but although they recognize the concept, they offer no solutions, simply crediting some god or making up a new god to encompass an unchangeable “fact of life.”
However, the Bible gives credit to the one time archangel, Lucifer, the father of lies. “Lying is Satan’s primary weapon against God’s children. He uses the tactic of deceit to separate people from their heavenly Father. Some of his more common lies are “there is no God,” “God doesn’t care about you,” “the Bible cannot be trusted,” and “your good works will get you into heaven.” The apostle Paul tells us that Satan “masquerades as an angel of light” (2 Corinthians 11:14), so that what he says and does sounds good and seems reasonable. But it is nothing more than a false appearance.” (https://www.gotquestions.org/father-of-lies.html ) It is an invasion of your privacy, a violation of your person not unlike statutory rape.
Perhaps you have some idea or ideas floating around in your head that you realize are not your own and perhaps obviously so and foreign to your mindset, your view of life, and your moral standards. We are ashamed of them. We blame ourselves. Yet, you are not the culprit.
“If you need wisdom, ask our generous God, and he will give it to you. He will not rebuke you for asking. But when you ask him, be sure that your faith is in God alone. Do not waver, for a person with divided loyalty is as unsettled as a wave of the sea that is blown and tossed by the wind. Such people should not expect to receive anything from the Lord. Their loyalty is divided between God and the world, and they are unstable in everything they do.” (James 1, New Living Translation)
Wherever you have picked up foreign thoughts, untrue thoughts, or even evil thoughts, there is a cleansing power far greater than anything you can imagine. In the Bible, cleansing of sin (or harmful things) is in the inner person — whether you think of it as “mind” or “heart” or “soul.” It is quite like the literal definition, “free[ing] from dirt, contamination or impurities” (https://www.thefreedictionary.com/cleansed)
Jesus breaks every chain. https://www.youtube.com/watch?v=-pD2zIuiC2g