“However, if he was, betcha his family knew it and were powerless to intervene.”
Chose NOT to intervene.
I know nothing about you except that, based solely on your comment, you have never had a family member with severe mental illness.
A family cannot force any person over the age of 18 into treatment. Mental illness, unlike physical illness, often makes its victims feel better, not worse, and they are unwilling to seek help.
Unless a family (or law enforcement, if it comes to that) can convince a judge that the individual is a danger to himself or others, there is no recourse. In olden days, these folks were locked in the attic. Now they are set loose on society. And there is noting a family, often victimized and aware, can do.
Over and over, these untreated loons hurt other people because there is currently no way to get them off the streets. The Capitol shootings a few years back, the West Virginia shooter, the Tucson shooter — they are among us, and there’s no legal way to act pre-emptively.
You are probably intelligent and caring, but you are ignorant of this very real problem in our society. I sincerely hope you never have to learn first-hand what it’s like for a family.