“I don’t understand your point of view, so I think you need therapy” is a very condescending point of view.

The comment above you is making the point of

Angry at society -> Take out anger on society

The shooter doesn’t give a shit about the victims as individuals; to him they’re just components of the society, or actors within the society that he thinks wronged him somehow. They’re part of the problem to him.

You’re assuming that the shooter was seeing and experiencing the world and interpreting it the same way you do. THEY DO NOT, they are mentally ill, and have different thought patterns to people who are neurotypical. They have managed to convince themselves that they don’t have a problem, that society is the problem.