“Most of these shooters have no criminal records. So that isnt working.”
Hate to burst your bubble but MOST if not all mass shooters have had some level of criminal involvement but are not charged due to mental issues. Many are referred to social workers, psych counseling but were are on “law enforcement radar”.
Plus, need more armed law abiding citizens to be prepared to stop a mentally ill person or criminal if they start to use a firearm. The police sure don't and cannot.