I just recently came across this 2010 story, about a would-be school shooter. He was stopped before anyone was hurt because he was quickly met by an armed response. The School Resource Officer was able to keep him in a standoff, until the Sheriff's officers arrived. Without that initial armed response, this could have been another deadly school shooting.
“He pulled out his gun and started pointing it at people,” Thacker said.
Cowan trained a .380-caliber semi-automatic pistol at Riden’s face [the principal], said Sullivan County Sheriff Wayne Anderson. Carolyn Gudger, the school resource officer, drew her gun, then shielded the principal’s body with her own.
Riden fled and Gudger inched back into the school, leading Cowan through the scattered pastel chairs in the empty cafeteria. It was a tactical move, meant to lure the gunman into a more contained place, Anderson said.