Police say 17-year-old Derek Shrout is a self-proclaimed white supremacist who wanted to commit hate crimes at Russell County High School in Alabama with homemade explosives.
Had his book of plans not been carelessly left where a teacher could find it, the sheriff says no one may have discovered the plot until it was too late.
Officials say the journal contained several plans that looked like potential terrorist attacks, and attacks of violence and danger on the school.
And in particular, there were six students specifically named, and one teacher.
After the teacher who found his journal notified authorities, police searched his home and found dozens of tobacco containers filled with shrapnel and holes drilled for fuses.
Investigators say Shrout was a step away from turning them into live grenades.
Police say they don't believe his parents had any idea this was happening.
Local media contacted Shrout's mother at his Fort Mitchell home but she did not want to make a statement.
When Shrout was interrogated by authorities, his explanation to them was that he had written a work of fiction and he never meant to carry out the plans in real life.
The sheriff disagrees.
Shrout is currently in the Russell county jail, charged as an adult.
He will be in court Monday to face a felony charge of attempted assault.