I wouldn’t count on that. The SRO at Columbine, who was in the parking lot at the time, exchanged shots with Eric Harris multiple times in the middle of the rampage with no effect, as did another deputy when Harris appeared at the door again. And during the school massacre in Erfurt/Germany, where mostly teachers were targeted (16 dead in 2002) the shooter killed the first responding police officer as he stepped from his patrol car..