In the wake of increasingly frequent school shootings, school districts across the country are using a combination of tools to try to prevent another tragedy. One of those is software that alerts administration officials to problematic social media posts.
The algorithm, which flags warning signs, is an attractive tool -- considering the disturbing social media posts by the Marjory Stoneman Douglas High School gunman prior to his shooting rampage. Seventeen students and staff members were killed.
Six weeks before the February 14, 2018 shooting, the FBI received a tip about the suspect's social media posts in which he talked about his gun ownership and desire to kill people. But that tip never made it to the Miami field office or its agents.
"It's tough and it's sometimes unfair to play Monday morning quarterback. But you have to ask the question, you know, what if the district had that?" said Greg Boulanger, who recently retired as director of public safety at Bristol Public Schools.
For the past five years, Bristol Public Schools has paid roughly $2 per student per year for a service called Social Sentinel. The software scans public social media posts within a geographical area for certain words, phrases and images that could indicate violence.
Boulanger said it's one of many tools the district uses to keep students safe.
Broward County Schools has a Special Investigative Unit that looks into threats on social media, spokeswoman Nadine Drew told CNN.
How Social Sentinel Works
Social Sentinel was founded by Gary Margolis, a former chief of police at the University of Vermont.
"We studied the language -- how violence is talked about," Margolis said. The company now has a constantly evolving, proprietary library containing "language of harm."
"It may be sentence structure, words, emojis, combinations thereof. So it's far more sophisticated than 'shoot,' 'bomb,' 'kill,'" he said.
Social Sentinel serves thousands of schools in 35 states, the company said. For each of them, its program is scanning the internet within geographical limits for posts that need to be flagged to school district officials.
Boulanger said he would get about three to seven alerts per day for a school district serving about 8,000 students.
Most of them are benign.
"The most frequent alert related to exams: If I have one more Latin exam, I'm going to kill myself," he said.
But since the district started paying for Social Sentinel five years ago, Boulanger has seen close to 20 situations that required intervention.
In a couple of instances, Boulanger described female students -- including one recent graduate -- who posted about harming themselves. He said a crisis team was able to intervene in those cases to help those individuals.
There have also been posts about threats to others.
"We received posts one morning ... about two girls who were going to throw down against another two girls who did something in the cafeteria. We were able to talk to the team here, and they went up and intercepted the activity that was about to play out," he said.
Texas City, Texas' Independent School District also uses Social Sentinel, and credits the service with possibly preventing violence at one school last September.
The company alerted district officials to a threat on Facebook and the person who posted it was arrested, according to CNN affiliate KPRC.
Concerns about privacy
A company called Geofeedia, which provides a similar service to police departments, was criticized by the American Civil Liberties Union for violating free speech.
The ACLU said Geofeedia helped police departments collect information about people's political activism. In 2016, Geofeedia's CEO said the company has policies in place to prevent inappropriate use of its software. By 2017, Facebook and Twitter had stopped giving Geofeedia access to their data.
CNN was previously a subscriber of Geofeedia but stopped using the service in late 2015.
Margolis said Social Sentinel is different.
"Whether it's a political protest or a cupcake festival, our system is agnostic to that. We are just looking for the language of harm," Margolis said.
Unlike Geofeedia, he said, Social Sentinel does not cater to law enforcement or municipalities.
Boulanger said from the school's perspective, "We're not going out and eavesdropping and looking to say, 'We don't like this student. So let's go look in their account.' First of all, I don't know how to do that."
School officials are only on the receiving end of alerts and cannot perform a search within the Social Sentinel program.
Boulanger said the district's goal is not necessarily to turn students over to police. The focus is on helping the student get to the root of the issue and bringing them back into the school community.
"I'm good with it. I'm good with what we have and how it works," Boulanger said.