Police in Florida have arrested an expelled student after thwarting what they called a “potentially catastrophic” plot to set off a bomb at his former high school.

A local police chief, Jane Castor, told reporters Wednesday the potential impact of the attack was something the city of Tampa has never seen and hopefully never will.

Castor said the suspect, 17-year-old Jared Cano, was arrested late Tuesday, and that he planned to carry out the attack at Freedom High School in Tampa on the first day of school next week.

She said he hoped to cause more casualties than those suffered in the 1999 attack at Columbine High School in Colorado. Two students at Columbine killed 12 classmates and a teacher in one of the deadliest school incidents in U.S. history. Both shooters later killed themselves.

Authorities arrested Cano after receiving a tip. In a search of his home, they found materials to make pipe bombs, a journal with drawings of rooms at the school, and statements apparently indicating his intention to carry out the attack.

Police say Cano has been arrested in the past on charges that include burglary and carrying a concealed weapon.