Sheldon Greenberg, a Johns Hopkins University education professor and former police officer, notes in a recent paper that armed security officers at schools have repeatedly failed to prevent or stop school shootings. Indeed, several law enforcement officers were present during the massacre at Marjory Stoneman Douglas High School but were unable to stop the mass shooting, which claimed 17 lives. If highly trained officers regularly fail in the fast-paced, high-stress context of a mass shooting, how can we expect teachers and school staff to succeed? How can we expect law enforcement to distinguish between a shooter and an armed teacher? How can an armed teacher distinguish between a shooter and a plainclothes law enforcement officer?