(CBS) — A 14-year-old student at Bolingbrook High School faces aggravated assault charges after he allegedly threatened a teacher with a BB gun.

Bolingbrook Police Sgt. Mike Rompa said the lockdown began around 8:30 a.m. Thursday and was over within minutes.  Rompa said the student “threatened harm” because of a grade the teacher had given him.

After making the threat, the student retreated to a washroom, where police found him.

Rompa said police lifted the lockdown after determining that the student acted alone.

Valley View Unit District 365U Supt. James Mitchem said in a statement that the incident was over in six minutes “due to the swift reaction of our security team, staff and students.”

Mitchem said no one was hurt and “every precaution was taken.”

Will County prosecutors approved felony aggravated assault and disorderly conduct charges.

Sgt. Rompa said the teen has been transported to the River Valley Youth Detention Facility for processing and medical evaluation.

Mitchem said in his statement that “supports” will be provided for students and staff at the school, and at other District 365U schools as needed.

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