I agree with these ideas for defending against these threats, however, I think the intention of this thread is to come up with valid ideas on preventing the threats to being with.
The thread says "solutions." That doesn't limit the solution set to only prevention. Just like medicine, you can do all the preventative measures you can, but eventually you will wind up sick. Once preventions fails, the solution is to fight -- the infection, or the shooter.
Everyone wants to believe we can prevent shootings. That's largely wishful thinking. We can prevent some, but a "system" isn't the way we do it. Systems fail, because PEOPLE don't take responsibility, just like this last episode.
Our legal system is set up to catch people AFTER they commit a crime. This last shooter was adopted, and his parents both recently died. He was diagnosed with autism. He was prone to outbursts and breaking things. He had issues controlling his temper. I read the Cops were called on him some 36 times. He posted threats, lots of pictures posed with guns, and photos of animals he killed. The FBI weas alerted 5 months prior. How many "systems" does it take to have prevented this shooting?
Prevention is not impossible, but the systems we need already existed once. Just like everything else in life, it's only effective if you actually participate and contribute to the process. Cops, mental health workers, school teachers, friends, family, neighbors, schoolmates, and even the guy who mows the lawn have to take responsibility for getting involved, or prevention will never happen. The shooter in Isla Vista, the South Carolina church shooter, and the Sandy Hook shooter are all additional examples where we can see in hindsight where the people who knew them failed. No system is going to prevent the next one without summarily stripping large groups of people of their Constitutional rights. We used to do that long ago until the 50s and 60s by involuntarily committing patients to mental hospitals. If you want a new-old solution that would actually help, that's a "rough idea" that is already a proven success. It'll solve much of the homelessness, drug addiction, crime and welfare cases in many areas by taking the mentally ill off the streets and out of homes to where they can be medicated, monitored and isolated from the public at large. Since we already know this is not really going to happen, the result is more of the existing problems while we search for new "systems" to prevent them.
This is the very definition of shooting yourself in the foot. We created these messes ourselves, and the solutions that worked before are now forbidden.