A single voice made a difference in preventing a possible school attack, according to an organization formed in response to the tragic events at Sandy Hook Elementary School.

On September 10, Sandy Hook Promise, a nonprofit, informed the Atherton, California police about a tip regarding a former student who had shared alarming Instagram posts related to a local high school.

The police took immediate action, temporarily securing Menlo-Atherton High School and a nearby middle school for an hour until they could locate the student. The investigation is currently ongoing.

Nicole Hockley, whose son Dylan was among the 20 children lost during the 2012 Sandy Hook tragedy, has dedicated herself to preventing similar incidents. She co-founded Sandy Hook Promise.

A free resource that teaches students how to recognize warning signs of violence and offers an anonymous reporting system.

“Each time we prevent an act of violence or a school shooting, it means another community is spared from the trauma I experienced,” Hockley expressed.

On Monday, Sandy Hook Promise announced their involvement in thwarting a possible attack on a school within the Sequoia Union High School District in Redwood City, California.

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“What we know is that a student saw a concerning post on a friend’s Instagram feed and reported it to our anonymous reporting system manned at our crisis center down in Miami,” Hockley said.

According to Atherton Police Department, the posts included images of ammunition. Sandy Hook Promise also claims the posts included an image of the school.

Law enforcement later detained the student.

The organization said the Menlo-Atherton incident is the 19th “credible planned” school attack nationwide” the system has prevented since its launch in 2018. About 5,000 school districts partner with the organization and tips are accepted via a mobile app, text, phone, or through a website.

“It is an example of one voice making a significant difference to a community and we really applaud that student for raising the alarm bells saying this is really concerning I think this person is planning to do something they need help,” Hockley said.

The district’s superintendent released the following statement:

“Nothing is more important to us than keeping our students and staff safe. In the wake of violence at other schools around the country, we take our responsibility to put prevention measures in place extremely seriously. Sandy Hook Promise has been a vital partner in helping our students and staff recognize warning signs of potential violence. We are grateful that Sandy Hook’s Say Something Anonymous Reporting system made swift action by local law enforcement and school administrators possible when a member of our community reported a potential threat against one of our schools recently. As a result of this program, we were able to keep students and staff safe.”

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Since its launch in 2018, the organization’s anonymous reporting system has stopped at least 19 credible planned school attacks nationwide.

“At a time when so many of us feel powerless of the epidemic of gun violence, or the epidemic of youth violence, this is proof that prevention works,” Hockley said.

KGO asked Hockley what fuels her work.

“This is what keeps me going, the love that I have for my surviving child and child that died – Dylan – but also knowing that we can create a safer future,” Hockley said.

The incident took place on the same day as a mass shooting in Evergreen, Colorado, where a 16-year-old shooter shot two students and then himself. The two students were in critical condition afterward. The school reopened this week for classes.

Hockley said they receive at least 200 tips a day from kids across the country.

School districts can partner with Sandy Hook Promise for free. Hockley encourages schools to visit their website.

Editorial Note: The Atherton Police Department clarified details ABC7 News in San Francisco received from Sandy Hook Promise about the potential threat. They say weapons were not recovered, and the social media posts contained an image of ammunition but no firearms were depicted.

ABC News contributed to this report.