An online threat against a Toronto high school was written by a student who attended classes with the same students police say he threatened to kill.

Police say, on Tuesday morning, a 17-year-old male was arrested for allegedly plotting an attack against Oakwood C.I. on the 27th anniversary of the massacre at Ecole Polytechnique in Montreal.

Authorities say they were alerted to the threat by an American who spotted a blog online that they traced to a Toronto District School Board computer and user.

Police sources told CTV Toronto they believe the suspect made open threats that he would go to the school with a machete and a hatchet to attack other students.

Officers then searched the suspect’s home, where they seized a machete, hatchet and other weapons.

TDSB Chair Robin Pilkey called the discovery “disturbing,” but added that the “good news part of this is that somebody was able to identify, they were able to trace it back to where it started.

By the time Oakwood C.I. students left school on Thursday, they had all been briefed by their principal about the alleged threat and the arrest of a 17-year-old classmate.

The incident has left some students rattled.

“It makes you think, if this one guy from the States didn’t find it, it could’ve escalated to something crazy,” one student told CTV Toronto.

Oakwood student Khadra Abdullahi said she’d “never think” that someone would try to attack students at her school.

Parents of students at the school are also concerned.

“My mom’s pretty shocked about it, she’s overwhelmed,” said student Jay Campbell. “She didn’t want me to come to school.”

The 17-year-old suspect cannot be publicly identified due to his age, but students who knew him describe him as “antisocial” and awkward.

“When he says that he has knives or whatever, you’re tempted to believe him because of how he acts and who he is,” said Oakwood student Jackson Scarf.

Police officers were on site at the school on Thursday, along with social workers.

“The message is that we’re here to support the students,” said school principal Steve Yee. “They’re the ones that really matter.”

The suspect has been released on bail under the supervision of relatives and police.

With a report by CTV Toronto’s Natalie Johnson