This is really a post-1960s problem with judges, who have been required by the fallout of long-ago decisions by the Supreme Court to prevent local authorities from locking up violent psychos in looney bins. I suspect you know this. Mental hospitals have been closed because of these policies, and the psychos, plus harmless crazies who just can't take care of themselves, are on the streets. It has never been allowed in civilized history to subsidize dangerously crazy people and let them run around unrestricted.
To make things worse, our crazies are treated as outpatients with drugs such as anti-depressants, which can cause side-effects that include mass murder. I've read that most US mass murderers of recent decades have been on anti-depressants--those who were not simply tripping on the Koran.
Trump is right to use this incident to help destroy the reputation of the FBI brass. They didn't follow their own procedures. He has to grind them down in the public eye first, so it doesn't look opportunistic on his part to start firing them now. He is using the media, so every time the enemedia screams how bad the shooting is "because Second Amendment," he drops into the conversation that the FBI caused it by failing to follow their own procedures.
The public outcry will keep building against the FBI brass, and in their weakened state, they can be dismantled by Congress and Trump. It's the way it has to go.
I just want him to start firing people. It’s not going to get better for him by ignoring this. The press will not love him, judges will not help him and the Congress will continue to ignore him and go their own stupid way. It’s frustrating.