L'Anse Creuse High School was shut down Tuesday morning after a former student, who now works at Selfridge Air National Guard Base, entered the building around 6 a.m.
Security concerns were raised because the man was dressed in camouflage.
Apparently the former student had just left work at the base and went to the school looking for a letter of recommendation. He was confronted by a cleaning person who told him the counselor he was looking for was not in the building.
The former student left the school without incident.
Sheriff's deputies were called in to check the building, but nothing was found.
Macomb County Sheriff Tony Wickersham tells Local 4 the former student was not armed and was questioned by police.
He was released.
Students who were being bussed to the school were taken to a safe location while the security sweep was being done.
L'Anse Creuse High School was closed for the day and ACT tests which were supposed to be taken by students Tuesday will have to be rescheduled.
"We still believe that the right decision was made by making sure our students were safe and we will do everything we can to make sure that they get their tests done and everything's all set," said L'Anse Creuse Schools spokeswoman Kelly Allen.
Classes at Graham Elementary and L'Anse Creuse Middle Central School were also canceled for the day.