They had a metal detector at Red Lake High School in Minnesota. And most surely, the adults knew the warning signs for kids who might erupt in violent ways. They knew to worry about the isolated kids, the bullied kids, the students who flirted with life’s darker sides. They knew much more than adults did that February 1996 when Barry Loukaitis opened fire in his Moses Lake school and ended forever school-safety naiveté.

But the metal detectors, the security guards and all the knowledge collected over the past “Columbine” decade, did not prevent the deadly day Monday on a northern Minnesota Indian reservation. Jeff Weise, 16, shot and killed nine others before turning a gun on himself.

The multiple-victim school shooting seemed even more jarring, because it had been awhile since the last one. There were none in 2004 and only three in 2003, and in those, only a couple of people died, as if that’s any cause for consolation. The U.S. Department of Justice reported in November that violent crime in schools has continued its steady decline in recent years. Students were “more likely to be victims of nonfatal serious violent crime away from school than at school.”

Still, the Red Lake shooting reminds everyone about the importance of zero tolerance on school campuses for weapons and the mandate to make public to parents and the media those times when weapons are confiscated on school property.

Most importantly, the Red Lake shooting is a reminder that worst-scenario planning is essential for teachers, students and administrators. These school-safety plans should be rehearsed with the hope they will never be needed and with the realization that even the best plans might be thwarted by young people intent on violence in their schools.

Weise was a troubled kid who wrote and spoke in violent imagery. He lived on an Indian reservation where there was a 40 percent poverty rate and a well-documented drug problem. Yet blaming his violence on this environment is as simplistic as blaming the Columbine High School tragedy on the privileged Littleton, Colo., upbringing of Eric Harris and Dylan Klebold. Much more was going on.

The shooters did have in common white supremacist beliefs and access to weapons of human destruction. The Columbine shooters built their own bombs. Weise helped himself to his law-enforcement grandfather’s stash. And they most likely had in common some mental illness. According to an April 2004 article at Slate.com, FBI analysts and psychologists recently concluded that Klebold was severely depressed and Harris was a psychopath, so intent on violence that “if he had lived to adulthood and developed his murderous skills for many more years, there is no telling what he could have done.”

The two shootings in two very different communities remind us once again that this kind of violence crosses cultural and demographic barriers. As the Red Lake community mourns its victims, the rest of the country mourns the fresh loss of innocence that happens each time a young person acts out in such a violent and radical way.