A private company in Washington, D.C. that monitors social media and flags potential terrorism threats may have helped thwart a planned attack on a Calgary high school, CTV News has learned.

The Tactical Institute, founded by Bob Dowling, a former FBI terrorism task force member, monitors social media around the clock on behalf of paying clients to flag potential threats to organizations and individuals.

Dowling told CTV Calgary that on Tuesday, his staff spotted a tweet that worried them: a photo of someone displaying a rifle with a scope with a tweet stating they were planning a shooting at their former school, Lester B. Pearson High School in northeast Calgary.

The tweet was not protected, meaning anyone with an internet connection could see it. After investigating the rest of the Twitter account, Dowling says his team was able to “put together a matrix that scored high enough for our team to reach out to the school.”

What concerned Dowling’s team was the direct nature of the threat and the fact that the Twitter user had made repeated threats against the school. They also noticed a geocode that indicated the account user was posting from a location close to the school.

Though the Tactical Institute does not work for the Calgary Board of Education, they chose to call the school to warn the principal of the social media posts.

The principal identified the Twitter user as a recent graduate of the school, and decided to contact police.

The Calgary Police Service confirmed to CTV News that one person was taken into police custody from a location off school property in connection with the investigation.

Officials with the Calgary Board of Education sent a notice to parents and guardians on Wednesday to address the alleged threats.

“School administration was made aware of an apparent threat by a former student of our school on social media. The school immediately called the Calgary Police Service (CPS) to assess the situation. CPS determined that there was no threat to the students or the school and our school day continued as usual,” the notice read.

“All threats of this nature are taken seriously and fully investigated. Each situation that arises requires an appropriate level of response to ensure the safety and security of students and staff. Should there be evidence that would require the school to initiate other critical incident protocols or procedures we would act quickly to enact those processes.”

Dowling says over the last five years, the Tactical Institute has helped intervene in 19 planned schools attacks, or in incidents in which weapons had been obtained by a suspect or suspects.

While threats against Canadian schools are not common, Dowling says his company located a threat against Balwin School in northeast Edmonton in September and alerted authorities. One suspect was arrested in that incident.

With a report from CTV Calgary’s Lea Williams-Doherty