Officials at Freedom High School in Tampa, Fla. are beefing up security for the start of the school year after police uncovered a bomb plot.
Authorities say the suspect, 17-year-old Jared Cano, was acting alone and had detailed plans.
"He also mentioned his desire to cause more casualties than were suffered at Columbine," Tampa Police Chief Jane Castor said.
Police investigators found materials for making pipe bombs as well as written plans for the first day of school in Cano's apartment.
"They indeed found a manifesto written by Jared that outlined, minute-by-minute, to include detonating explosive devices through the school," Castor said.
Authorities believe Cano planned to kill 30 students and two administrators at Freedom High.
School officials expelled the teen last April and he had not enrolled for this year.
Tampa police periodically checked on Cano because of his troubled past, including arrests for marijuana possession and carrying a concealed weapon.
His Facebook page reveals a young man intrigued with getting high and apparently violence.
His favorite quote listed on his Facebook profile was, "Lessons not learned in blood are soon forgotten."
Freedom high officials still plan to start school next week. But with a new level of anxiety in the air, authorities say they'll take extra precautions to make sure everyone feels safe.
"We still are going to have an increased security presence," Freedom High Principal Chris Farkas said. "Tampa police have agreed to have people here for our open house and first day of school just to make people feel safe."
Authorities are encouraging more would-be tipsters to report such plots. A 2004 study found that in 80 percent of school shootings, friends or peers of the attacker knew about their plans, but said nothing.