That's the big problem. Apparently some years ago they closed a bunch of psych hospitals so there is no place for these people to go. I work in an ER, psych patients come in, we have to house them until we find a bed, go through an entire battery of tests, it takes up an emergency room (small hospital we have very few ER beds available), someone has to watch them constantly and document their behavior every 15 minutes, sometimes it takes 24 hours to find a bed and sometimes they have to be shipped clear across state by ambulance therefore taking up EMT time as well. Sometimes there are no beds available period and they eventually say the person is okay, promises not to hurt themselves or others and so they have to let them go. It's a bad situation.
https://www.motherjones.com/politics/2013/04/timeline-mental-health-america/
https://www.atlasobscura.com/lists/abandoned-psychiatric-hospitals
That's the big problem.
Community Mental Health Act of 1963 -- "mainstreaming" severe mental illness.
Instead of being treated, sometimes involuntarily, many end up in prison or jail. And they aren't treated at all.
I find it hard to believe that jailing the mentally ill is cheaper than treating them in mental hospitals.
And mass shooting victims aren't the only casualties of this. They are probably only a tiny fraction. Look at the Hepatitis A epidemic in California, spread by homeless people defecating in the street.
My dad commented years ago on what it took in the late 1930s to institutionalize a relative (rural Alabama). You basically wrote a letter to the county judge...found two witnesses to swear in front of the judge, and then the judge would send a crew out to pick up the guy or gal. There would be an interview with the individual and then they’d be packed off to a state facility.
All of that ended in the 1960s because of the shame of the condition of state facilities (throughout the US).
I would take a guess that throughout the entire US...you could be talking about half-a-million folks who need to be institutionalized. The odds of this being understood by the general public? Zero.