I suspect that I am in a minority, but if he had a learning disability (ASD?) , or a personality disorder or undiagnosed psychiatric condition, then he has been let down. Yes, what he did was horrendous, my heart goes out to the deceased and their families. I admit quite freely that I cried when I saw that a 3-year-old had been killed. But I also feel that something catastrophic has happened to the perpetrator in his life; we don't KNOW what that might be, but I hope that over time there are some answers.
If he does have a learning disability, and he does, by some reports, seem to have attended a special school when young, then that might give some clues.
I can only tell you about my son, who has an ASD. He was badly bullied at school, and despite what he told the teachers, he was labelled the perpetrator of the bullying. He would sit all day with people doing awful things to him and when he lashed out he was punished. it seems that because the bullies were female or from an ethnic minority, they were deemed to be incapable of being bullies. Eventually, a well respected teacher saw the whole of an episode of bullying, and that stopped the bullies in their tracks. He was then seen, quite rightly, as the victim, but oh my god, did it take a long time! As a consequence of this my DS has been left with severe anxiety, I have spent the last 2 years trying to get some help, we were just getting somewhere when the pandemic hit, so we are back to square one. And I won't even start on the knock-on effects to the rest of the family. It seems almost impossible to get any serious help, waiting lists are just ridiculous and from where I am standing mental health services have always been a Cinderella service. When people with learning disabilities leave education, it seems that too often they are abandoned. No-one wants to know.
Why am I saying this? Because we don't know what was happening; we don't know if the shooter has himself suffered. We don't know if he had some psychotic episode, we don't know if he just wanted to end his life and go out with some infamy. We don't know if he was evil or ill. Of course, he shouldn't go out and kill 2 men,2 women and a toddler. I am not defending his actions, but perhaps we should understand that there many people who don't fit into the model of society that we have, and they don't get any help either.
I know all of this is a long, probably incoherent ramble. It's clearly my own frustration coming out, but I do think I might have a bit of insight into why some people just snap. Instead of condemning him, I want to await some answers from the professionals who should have dealt with him.