The Associated Press lies. Most of the mass murderers were on drugs. They were able to buy weapons by lying on the 4473 forms, because the police didn’t bust them for drugs.
Universal background checks won’t fix that. After both political parties attack the Constitution by passing universal background checks and/or a red flag putsch, lax policing will allow the drug addicts and dealers to continue murdering people.
You make a most excellent point: “Most of the mass murderers were on drugs.”
Another common theme among mass murders is that they have had some negative contact with a police agency as a juvenile, and since juvenile records are sealed when said juvenile turns 18, they cannot be accessed in the NICS background checks.
That is an area that should be investigated. Perhaps ALL serious juvenile convictions (i.e., those that, were the perp an adult, would keep him/her FRom being able to legally purchase a weapon?) should be reported for the purpose of denying a weapon purchase?
Being busted for ANY drug use should be an instant disqualifier!