Since the shootings at Colorado's Columbine High School in 1999, in which two students killed 12 classmates and a teacher and wounded 26 others before killing themselves, police nationwide have adopted "active shooter" policies where officers are trained to confront a shooter immediately.
"The goal is to stop it, from the law enforcement side, stop it as quickly as you can because we know with an active shooter if you don't stop it, more lives will be lost," Canady said.
Confronting a shooter certainly carries risks.
In Sparks, Nev., math teacher Michael Landsberry was killed in November after calmly approaching a 12-year-old with a gun and asked him to put the weapon down, witnesses said. The boy, who had wounded two classmates, killed himself.
Weingarten said more emphasis needs to be placed on improving school cultures by ensuring schools have resources for counselors, social workers and after-care programs. Many of these kinds of programs were scaled back during budget cuts of recent years.
Experts have said a healthy school culture can prevent such incidents and even lead students to tell adults about classmates who display warning signs that they could commit such violence.
Education Secretary Arne Duncan told reporters Thursday that he also believes strong mental health support systems in schools are important. But he said schools are doing a "fantastic" job with school security and often schools are the safest place in a community.
He blames easy access to guns as a root cause of the problem, but that's a contention that doesn't have widespread agreement as gun control continues to be a hotly debated topic.
"This is a societal problem, it's not a school problem," Duncan said.
Bond, who is now the safe schools specialist with the National Association of Secondary School Principals, said there was a time when he believed school shootings would stop. He's come to a sad realization that gives him a "sick pit in my stomach" that they won't end, he said.
"Schools are still part of the American society and the American society is violent," Bond said.