The Williamstown Police Department responded to swatting incident at Mount Greylock Regional High School after someone called in a hoax phone call threat to the school on April Fools Day.

WILLIAMSTOWN — Mount Greylock Regional High School was placed on lockdown Wednesday morning after someone called in a hoax threat reporting an armed man heading into the building.

The threat was called in directly to the school, prompting administrators to implement security protocols, Williamstown Police Chief Michael Ziemba said in a news release.

The school notified police at about 10:15 a.m. Officers searched the school and nearby areas and found no evidence to support the threat.

The caller's hoax threat was that an unknown male was in the parking lot and was heading into the school with an assault rifle, Ziemba told The Eagle.

The school returned to normal operations at 11:03 a.m. Additional public safety resources will remain on scene for the remainder of the school day and the investigation is ongoing.

Police asked anyone with information to contact the Williamstown Police Department at 413-458-5733.

Ziemba said it was unclear if the hoax threat was made as an April Fools' Day joke, but that "the recipient of the call did not interpret it as such."

Whatever the caller's motivation, Ziemba said the hoax was a "textbook" example of "swatting," and was illegal.

"Swatting is a dangerous, illegal hoax where perpetrators make false emergency reports—such as bomb threats or active shooters—to provoke a heavily armed law enforcement (SWAT) response to a target's address," his news release said. "It is a criminal act of harassment or retaliation that puts victims, officers, and the public in immediate physical danger."

Williamstown officers, assisted by North Adams, Lanesborough and Massachusetts State Police departments, conducted the search of school grounds, and the Williamstown Fire Department and Northern Berkshire Emergency Medical Services assisted.