School police arrested an Atlantic Coast High School student within three hours after the student posted a threat to shoot up the school on social media, according to the district.
After initiating a code yellow security status during Thursday morning's investigation, the school returned to normal operations by noon.
In a message to parents, Atlantic Coast Principal Michael George wrote, "While this specific threat was unfounded, we always take these situations seriously and never dismiss a threat as a prank or a joke. I do want to emphasize that the individual responsible for making the threat is being arrested by the police.
Please take this opportunity to coach your children on appropriate behavior on social media. A single post of this nature can have life changing consequences, and we will take disciplinary and legal action when these threats are made. I appreciate your patience and cooperation as we have worked through this situation, and I look forward to a great day of school."
The district says, "We also encourage students, parents, and community members to report threatening activity to law enforcement. You can call police directly or you can do so easily through the Fortify Florida mobile app. If you haven’t done so already, please take this opportunity to add this threat reporting app to your cellphone."
Atlantic Coast High School is in Southeast Jacksonville.