GREENWOOD VILLAGE, Colo. (KDVR) — A threat made to Cherry Creek High School prompted the three schools on the campus to be put on a secure perimeter late Thursday morning.

The Cherry Creek School District said the threat was sent to someone who lives out of state via a social media message from an unknown person, threatening to “shoot up the school.”

Police are investigating the source of the threat but have not given any details.

A message was sent to parents saying Bellview Elementary, Campus Middle School and Cherry Creek High School were placed on a secure perimeter around 11:30 a.m.

According to the CCSD website, “Secure perimeter means that all students and staff outside the building are brought inside, all exterior doors are closed and locked and normal activity continues inside the building.”