Damnatio memoriae: "The sense of the expression damnatio memoriae and of the sanction is to cancel every trace of the person from the life of Rome, as if he had never existed." (source: Wikipedia)
Many of these mass shootings seem to be a spurred by a desire for fame, for recognition. I propose that the media be barred from publicizing a shooter's name or showing his picture. Deny them their craving for glory. Instead call them "Coward A", "Coward B", etc.