TAMPA, Fla. – Tampa police have arrested an expelled student after thwarting what they deemed a potentially “catastrophic” plot to set off a bomb at his former high school and cause mass casualties on the first day of classes next week, authorities said Wednesday.

Police Chief Jane Castor said Jared Cano, 17, had threatened to plant a bomb at Freedom High School in north Tampa and detonate the device when students return Tuesday.

The suspect was arrested Tuesday night after someone alerted police to the alleged plot.

Castor told a news conference that the alleged bombing plot was planned minute by minute and the intent was to cause more casualties than the 1999 Columbine High School massacre, which resulted in 13 deaths before the two shooters killed themselves.

Castor said police and the school system “were probably able to thwart a potentially catastrophic event, the likes of which the city of Tampa has not seen, and hopefully never will.”

At Cano’s apartment, police discovered materials to make pipe bombs, shrapnel, plastic tubing and timing and fusing devices, along with a fuel source, Castor said. Police also said they found a journal containing schematic drawings of rooms inside the school and statements about the teenager’s intent to kill.

The Tampa high school shares a cafeteria with its neighboring middle school, increasing the potential threat to hundreds of additional students, officials noted.

The plot targeted specific school administrators and any students who were nearby, police said. Authorities did not name the administrators nor would they disclose who tipped them off about the alleged plot.

Cano’s mother consented to a police search Tuesday evening, Castor said. In addition to the bomb-making materials, police reported they also found a marijuana-growing operation.

Cano faces felony charges of possessing bomb-making materials and threatening to throw, project, place or discharge a destructive device. Additional felony charges include cultivating marijuana, possession of drug paraphernalia and possession of marijuana, authorities said.

Authorities said Cano had several arrests as a juvenile. Charges have included burglary, carrying a concealed weapon, altering serial numbers on a firearm and drug possession. All had been either dismissed or no action had been taken.

Police Maj. John Newman said Cano had been on a list of juveniles who police checked on from time to time because of their brushes with the law.

The St. Petersburg Times reported that prosecutors, at a hearing Wednesday, said that when Cano was arrested he repeated his plan to detonate a bomb and cause mass casualties at the school.

The Times reported that Cano tried to speak when he appeared before a judge Wednesday morning but was quickly hushed by a public defender standing beside him.