School districts across Florida are using a technology to scan social media in hopes of preventing a mass shooting.

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The technology is designed to detect warning signs from students through threat indicators on troubling social media posts.

It's called Social Sentinel, software that would cost the same as a cup of coffee per year per student.

A year ago today, 17 people were fatally shot at Marjory Stoneman Douglas High School in Parkland, Florida.

After the shooting, investigators combed the social media profile of suspected shooter Nikolas Cruz and found a disturbing online footprint.

In the months before the shooting, investigators said he made online posts about his aspirations to become a professional school shooter, and posted photos of himself with guns on Instagram.

Investigators said the warning signs were there but somehow missed.

Social Sentinel is being used across the country to detect troubling online posts.

“Roughly 40 percent of school violence is shared on social media. We’ve built a library of harm that has hundreds of thousands of threat indicators,” said Gary Margolis, the founder of Social Sentinel.

Social Sentinel finds information schools can use by scanning public posts on sites like Instagram, Twitter and Tumblr; if something is found, the school will receive an alert and can begin investigating the post.

The company said no districts in Northeast Florida use the technology, but some Central Florida schools do.

Districts in more than 35 states are now using the technology to help protect 4.5 million students.