I think you're touching on the heart of the situation, but I can't entirely agree with your conclusion. As the parent of a mentally ill young man, I can tell you firsthand that it's not as simple as coming up with a system for locking up people with problems or red flags. As we did in the past, we would sweep up way too many harmless people and separate them from their families, making things much worse for those individuals while doing nothing to protect the public. If we can find a way to determine who is a threat and who is not accurately, perhaps it could work, but that's not how these things ever work. Legislation will be too broadly drafted (as it always is), and sick kids will be placed into terrible environments in which they don't belong. It has been a long-held notion in this nation that one is innocent until proven guilty, that we would prefer a guilty person go free than lock up an innocent one. I have always believed strongly in this and still do, especially when we're talking about people with mental illness.
The answer is not just to start locking up sick people, although we need to start treating mental illness seriously in this country. If you're not wealthy, your kids will have difficulty getting meaningful treatment. That's a place we can start right there. Mental healthcare reform. Force the fucking insurance assholes to cover mental health services and require mental health providers to accept insurance for payment. We're completely broken as a nation in this area, but we could make a significant difference with relatively simple legislation. Acts like the one this week can be better prevented not by locking people up but by making treatment available in the first fucking place. The other thing that would do more to stop this crap than anything else, but won't happen because Americans are dumber than a bag of rocks/hammers/dildos, is to get rid of fucking guns. All of them. Now. But as Brisket has mentioned repeatedly, we have the country we want. What we want is to divert attention from the real problem by demonizing mentally ill people because a large segment of our population is struggling with an inferiority complex and feels better being surrounded by weapons. I think these discussions routinely focus on the wrong mental health issues, personally. Obsessive behavior around guns is the more significant mental health problem, but it's not ever discussed at all.
A bunch of patriots think an America utterly beholden to the insurance and gun lobbies is the best version of America. And who do you think loves the more recent narrative regarding mental illness? Another large industry with significant lobbying power, perhaps? It's all fucking bizarre and should be shameful to anyone who truly believes in the notions that this nation were founded upon. King George, thy name is now industry.