Waseca had a close call this week. A 17-year-old student at Waseca High School was arrested and charged with planning to kill his family, and continue the massacre at school with homemade bombs and firearms. He told police he had hoped to kill as many students as possible before the SWAT team killed him.

Police stumbled onto the plot when a woman saw John David LaDue entering a rented storage shed. She thought he looked out of place and called police, suspecting a burglary. Instead, they found LaDue with pounds of bomb-making chemicals, pounds of nails and ball bearings intended for shrapnel. They found three completed bombs in his bedroom at home, along with guns and a detailed, written plan for the attack.

LaDue does not fit the familiar profile of a troubled teen. He wasn’t a loner, wasn’t the vicitm of bullying, wasn’t considered odd or unusual. He was a good student, well-liked, a budding guitar player who always thanked his instructor after his lessons.

And he had a fascination with the Columbine High School and Sandy Hook Elementary shooters. His plans show how he studied their methods in hopes to kill even more.

The old questions arise: What impells someone like that to want to kill? How do they amass large quantities of explosives and ammunition without being noticed? Was there anything in his behavior that should have served as a warning? How can we identify potential mass killers before they kill?

In this case, someone saw something unusual and called police. That, for now, may be the best advice all of us. We have to be aware, alert and willing to make the call.