The 10-minute lock-out, put into effect after a notification from the Bethel Police Department, affected all of the town's five public schools on the campus.
In a lock-out, no one is allowed to enter the buildings, but classes continue regularly inside.
"All students and staff were safe during this time," the district said in the message. “The staff did an excellent job with the implementation of our safety and security protocols."
No further information was released on the incident.
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