Transcript for Teen Allegedly Obsessed With Columbine Arrested For Suspected Bomb Plot
We're learning a lot more about that alleged bomb plot stopped by police in Minnesota. They say a teenager obsessed by columbine planned to kill his family and then his high school. The woman who called the cops is revealing what raised her suspicions. Alex Perez is in waseca, Minnesota, this morning. Alex, good morning to you. Reporter: Good morning, Dan. Prosecutors are seeking to charge the teenager as an adult. School officials here have announced a few changes, hoping to calm fears. Overnight, worried parents packed waseca junior and senior high school, as the superintendent released new measures. Including magnetic locks at schools. Your quick thinking may have saved lives. How does that feel? It makes me feel good. I'm glad I trusted my gut. Reporter: Chelsea is being hailed a hero. She called 911 Tuesday, when she noticed 17-year-old John David Ladue, cutting through her backyard, instead of the sidewalk, to get to this storage unit. You see him walking through your backyard, that made you suspicion. He made himself look suspicion by trying not to be seen. Reporter: They found Ladue inside and the makings of a massacre. Ammo and materials to make nail bombs. Investigators say Ladue was just days away from carrying out a plot that involve D killing his family, setting a fire to distract police and then, heading for the high school. He planned to set off numerous bombs during the lunch hour. Kill a resource officer as he responded to help. Set fires and shoot students and staff. Reporter: Ladue allegedly admitted to setting off explosions in nearby areas, as preparation for his deadly attack. And investigators say Ladue had allegedly been plan the attack for about ten months. And sketched out every detail in a journal. A journal in police hands. Thank goodness that witness acted on her intuition. Now, a deadly virus thought
This transcript has been automatically generated and may not be 100% accurate.