You didn't ask a question. You saw behaviour that you didn't understand and immediately made an assumption: it must be the result of mental illness.
You are saying two things:
1) He is violent because he has a mental illness.
2) People with mental illness are violent because of their illness
The reality is very simple: he was a violent man. He had always been a violent man. He had a long history of violent behaviour. He doesn't have a long history of contact with MH services, and he never had (as far as I know) any contact with secure MH units[1]. Some men are remarkably violent, but most of them know exactly what they're doing and they're not controlled by an illness.
The prevalence of violence, and mental illness, means that obviously there's some overlap between "people who are ill" and "people who are violent", but you need to be really careful not to say "the violent people in that overlap are violent because of their mental illness".
When looking at predictors of violence we see that mental illness doesn't give you much if any predictive power.
Substance misuse does; previous episodes of violence does; and any (especially all) of these combined does.
The reason it's important to avoid incorrectly linking violent behaviour to mental illness is seen in the stats of people shot and killed by US police: about half the people shot and killed each year are people with mental illness. The vast majority of them pose zero risk of harm to other people, maybe some risk to themselves, but they get killed because people like you keep pushing the "mental illness == violent and dangerous" myth.
I didn't ask a question because I stated my opinion as to the single mass-murderer's state of mental health. I made no comment about the larger mentally ill community.
Just by virtue of his actions, and also because the news mentioned that he's been in jail, I think he's probably got some kind of mental illness or thought disorder. I could be wrong or I could be right, but for the moment I'm going to stick to that opinion.
I never said all mentally ill people are violent or dangerous, because I don't have some concealed anti-mentally ill agenda.
I do however have a bias in thinking that mass-murderers are generally mentally ill, and a quick google implies I'm factually correct in having that bias.
> He doesn't have a long history of contact with MH services
Hmm. Just the fact that he has had contact with mental health services strengthens my opinion that he's probably mentally ill.
As you've said yourself, some mentally ill people are violent and dangerous, some are not. I am aware of that.
When people are around trigger-happy US cops with guns pointed at them, they get shot, which is no surprise with such a militarised police force. Unfortunately that's the society some people live in.
If cops shoot mentally ill people, that's a problem with the cops and the society that tolerates that behavior, not me for speculating about whether or not a single mass murderer has a mental illness or not.
Don't try to imply that my opinion of a single case is in some way responsible for trigger-happy police in a country I don't even reside in.
I'm neither in the US, a cop, nor mentally ill so none of those are my responsibility.
Once again, I'm talking about this particular mass-murderer, and I think he's probably mentally ill. Nothing you have mentioned has swayed me from that opinion.
I don't think it's ignorant to ask the question if someone who did that is right in the head.