" I don't know anything about the shooter du jour, but in the past we learn that these people tend to get their guns legally, and tend to fly under anyone's radar untilt they burst - literally - onto the scene, guns ablaze. "
Wrong, Stinky.
The vast majority of gun- related crimes, including most mass shootings, are committed using guns that the shooter owned illegally. Often, the closest to a mass shooter "Getting their guns legally" is the shooter STEALING guns that were legally owned by a family member (i.e. the Sandy Hook shooter used guns that he stole from his mother), in which case, the answer is simply to try and encourage legal gun owners to more securely store their guns, especially if they know one of their loved ones is mentally unbalanced and displaying the warning signs of getting violent.
Again, I say the best way to help prevent future shootings is by starting some kind of awareness campaign to help better educate the public on the warning signs that a person may be at risk of engaging in violent acts, and encouraging them to get off their butts and do something about it if they see a friend or family member displaying those signs.
A noble idea but difficult to put into practice. Example: A couple is getting divorced. The wife calls the police to tell them her husband is mentally unstable and abuses the children. This could be the furthest thing from the truth, but the police have to act. The husband has to give up his guns (and may never get them back, seriousness of the charge and all that, regardless of facts) and go to counseling etc.
2 guys wander the streets of some city. They both mumble to themselves, do a little panhandling, but otherwise bother no one. One is going to be violent, the other isn't. Do you pull them both off the streets?
And finally, who is the arbiter of who is, and who isn't, violent? My money is on someone who is anti-gun and their final word decides. The more "mentally" violent people he/she finds, the more guns the police confiscate.
It was suggested in a thread at the DUmp some time ago, just wanting to own a gun was a sign of mental illness and those people should be denied the right to own one. The only people who could own a gun, according to that thread, were people who didn't want one, proving they were sane.
I agree some sort of pro-active measures need to be taken if someone is believed to be exhibiting signs of violence, and very, very few families would take those measures against a family member, but it becomes a slippery slope. Just my opinion.