The student, whose name was not released because of his age, was arrested about 9 a.m. after officials at Ocean Shores High School found he had written a note under a false name that included threatening words about a teacher and brought the boy to the school administration office, said Oceanside police Lt. George Darrah.
"During a health and safety check, the 17-year-old student was found to have an empty handgun holster inside his pants," Darrah said. "The student was also found in possession of a journal where he wrote about killing other people during a school shooting at El Camino High School."
The boy was formerly a student at El Camino, Darrah said.
After the boy was taken into custody, detectives and school resource officers executed a search warrant at his home, where they found "more hand-written documentation threatening violence towards people at the school, replica guns and body armor" in his bedroom, Darrah said.