“Lockdown” means a circumstance in which the persons on school property are restricted to the interior of a school building and isolated from threats until the school property and surrounding vicinity are deemed to be secure by:
1. If the school district has school police officers, the chief of school police of the school district or a person designated by him or her; or
2. If the school district does not have school police officers, the school resource officer or a person designated by him or her or, if the school district does not have school resource officers, a local law enforcement agency.