There have been precursors in virtually all these incidents that no one acted on. Bureaucratic failures, police failures, school official failures, family failures, friends failures to report it. No gun law after the fact is going to stop this.
Adam Lanza (Sandy Hook) was deeply disturbed yet his mother bought and gave him access to firearms. How could a gun law prevent the stupidity of his mother? She paid for it with her life. Unfortunately others did too. And still others have been forced to give up their constitutional rights because of it.
So if we're going to take action, let's have a national debate with the FACTS. The Dems always want to legislate immediately when emotions are high and nobody reds the bill. The facts are that we already have Red Flags with these people.