Northland High School in Columbus, Ohio, is under lockdown Tuesday morning after a school employee reported hearing a gunshot on his way to work.

10TV reported that the employee – an administrator – called police, prompting the lockdown at Northland HS.

The Columbus Police Department said a Northland student also heard the shot and that the student also said he heard a classmate threatening to shut down the school. The student said the classmate then fired a shot in the air outside the Ohio school.

The student who may have fired the shot has not been located, according to 10TV, but police have set up a milelong perimeter in hopes of finding the suspect.

The Northland High School website does not have any information on the lockdown as of Tuesday morning.