RAPID CITY, S.D. (KELO) — Public schools in the Rapid City Area School District are closed Friday after a threatening social media post, police say.

Rapid City Police say the school district has been made aware of a nationwide TikTok trend and a post about “North Middle School” this week.

After investigating, police determined that the post about North Middle School originated in Iowa.

Police say they are working with the school district to ensure the safety of students and staff.