Authorities in Tampa, Fla., have arrested a 17-year-old after discovering via a tip that he allegedly planned to set off explosives and kill dozens of students at his former high school, officials said Wednesday.

Police found explosive materials in Jared Cano’s home, as well as a manifesto outlining a minute-by-minute plan detailing specific targets at Freedom High School, Tampa Police Chief Jane Castor said. Cano allegedly hoped to kill two administrators and about 30 students, exceeding the level of violence associated with the 1999 school shootings in Columbine, Colo., Castor said.

The attack — scheduled to take place at the start of the school year — would have been “a potentially catastrophic event,” she said.

Cano was expelled from Freedom High School in March 2010 after what Principal Chris Farkas described as an “off-campus incident.”

Lewis Brinson, the Hillsborough County assistant superintendent for administration, said “inappropriate behavior” led to Cano’s expulsion, but did not provide further details.

Castor said police received a tip regarding Cano’s plans, though she declined to name the individual who provided the information.

There is no reason to believe that anyone else was involved in the plan, Castor said, noting that no organizations were mentioned in the manifesto.

She stressed that Cano’s family has been cooperating with authorities and said there is no evidence the family was aware of the plan.

“I’m not sure that his plot was realistic to carry out,” Farkas told reporters Wednesday. But still, word of the planned attack left members of the school’s community shaken and shocked, he said.

“You hear about things nationally, but I think that to have it here in your backyard … shock is probably one of the first things (you feel), and then I think there’s fear that goes along with it,” he said.

Police have agreed to step up security for the first day of school — scheduled for Tuesday — “just to make people feel more safe,” Farkas said.

The fact that a tipster led to the former student’s arrest in Tampa shows the importance of schools nationwide building a relationship with their communities, said MaryEllen Elia, Hillsborough County Public Schools superintendent.

“Someone realized it was very important that they share this information and that they help us address this issue,” she told CNN. “I think it’s very important that we make sure that people are aware that this kind of situation could occur anywhere.”

CNN’s Brooke Baldwin contributed to this report.