Panic at Massachusetts prep school caused by police responding to hoax threat

An active shooter was falsely reported at St. John's Prep in Danvers, causing a lockdown and major police response.
During a sweep of the school, a police officer's gun accidentally discharged, elevating the response to an active shooter situation though no threats were found.
The school was placed on lockdown, with some students fleeing, but no injuries were reported.
The incident is believed to have been a "swatting" hoax call intended to provoke a large police reaction.
Classes will resume Wednesday as authorities continue to investigate the source of the false reports.