SAN MATEO (CBS SF) — San Mateo police announced Monday that they arrested a teenager who posted a threat to shoot up Serra High School on social media last Friday.

On Mar. 22 at 5:35 p.m., police received an anonymous tip about the school shooting threat. At the time, officers were unable to identify the caller or verify the credibility and specific nature of the threat. Police said they worked with Serra High School administration to complete a “comprehensive and intense” investigation.

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Police increased their presence in and around the school throughout the weekend by adding more uniformed and plain-clothes officers in the area.

Officers identified and arrested the suspect, a 16-year-old male San Francisco resident, on Monday morning for making criminal threats. He was booked into Hillcrest Juvenile Hall.

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A threat assessment was conducted in collaboration with the San Mateo County Board of Education Threat Assessment Team to determine the threat level and to decide how to proceed with the involved teen.

San Mateo police are asking parents to speak with their children about the seriousness of threats posted to social media and to encourage them to come forward immediately when threats are seen.

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SMPD is actively investigating this incident and is asking anyone with information to contact San Mateo Police Detective Sergeant Lee Violett at (650) 730-9748 or by email at