South Carolina ? A high school senior collected enough supplies to carry out a bomb attack on his school and detailed the plot in a hate-filled diary that included maps of the building and admiring notations about the Columbine killers, authorities said Sunday.

Ryan Schallenberger, 18, was arrested Saturday after his parents called police when 10 pounds of ammonium nitrate was delivered to their home in Chesterfield and they discovered the journal, said the town’s police chief, Randall Lear.

The teen planned to make several bombs and had all the supplies needed to kill dozens at Chesterfield High School, depending on where the devices were placed and whether they included shrapnel, Lear said. Ammonium nitrate was used in the Oklahoma City bombing in 1995 that killed 168 people.

“The only thing left was delivering the bombs,” the police chief said.

Schallenberger kept a journal for more than a year that detailed his plans for a suicide attack and included maps of the school, police said. The writings did not include a specific time for the attack or the intended targets.

Sunday was the ninth anniversary of the Columbine High School massacre, in which two teens killed 13 people before committing suicide.