A police officer accidentally fired their gun while investigating a report of an active shooter at a school in northern Massachusetts, causing a heightened law enforcement response for what turned out to be a hoax, authorities said.

While alone in a school bathroom, a local police officer inadvertently discharged their firearm, the Danvers police department said in a Facebook post. Local and state police had responded to a report of someone with a gun at St. John's Prep at about 2 p.m. Monday, and the sound of the gunshot "elevated the situation," police said.

"Typically, we would have probably just kept our patrol force investigating initially, but when we had that report (of a gunshot), we didn’t know where it happened at originally or how it occurred, so we had a larger response," Danvers police Chief James Lovell said at a news conference after a sweep of campus found no shooter and no victims.

Some students at the all-boys Catholic school ran into the woods near campus, school officials said.

FORMER MA NAVAL OFFICER SENTENCED TO 18 MONTHS FOR THREATENING EX-WIFE, HER MOTHER 

The episode came two days before the one-year mark of the shooting at Robb Elementary School in Uvalde, Texas, which claimed the lives of 19 children and two teachers.

"This is everybody’s nightmare," St. John's Head of School Edward Hardiman said. "Every parent, in the context of our culture today, is concerned that things like this can happen."

The investigation is now focused on who made the hoax call and what caused the officer's weapon to discharge.

The school remained closed on Tuesday and a state police spokesperson said there were no new developments.