At least 68 schools that experienced a school shooting employed a police officer or security guard; in all but a few, the shooting ended before any intercession. Security guards or resource officers were present during four of the five school shooting incidents with the highest number of dead or injured: the 1999 Columbine High School massacre in Colorado, the 2018 Stoneman Douglas High School shooting, the 2018 Marshall County High School shooting in Kentucky, and the 2001 Santana High School shooting in California.