SUNNYVALE (CBS SF) — A 17-year-old Fremont High student has been arrested for making threats on social media targeting his classmates, Sunnyvale authorities announced Tuesday.

The Sunnyvale Department of Safety said they were tipped to the threats that referred to potential acts of violence against the students when they returned to class Tuesday from the Labor Day holiday.

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Security was increased at Fremont High on Tuesday, but investigators believe the student was acting alone.

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The student was in custody and could face felony criminal threat and hate crime related charges.

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School officials said they would continue to update parents and students as the investigation continues.