CLAREMONT — Four students are facing expulsion and some may be charged criminally after a gun scare that touched off a huge police response and sent Stevens High School into lockdown on Tuesday afternoon.

Multiple Upper Valley police departments, along with state police and sheriffs, descended upon Stevens High shortly before 1 p.m. after a student reported to administrators that “they had seen a Snapchat post showing four Stevens High School students with a gun inside the school,” SAU 6 Superintendent Chris Pratt reported in an email to parents on Tuesday afternoon.

Other schools in the city were also notified and put into lockdown out of precaution, officials said.

During a sweep of Stevens High, police located four students who were not adhering to the lockdown, including one who was found to be in possession of a “BB gun,” according to Pratt.

Claremont Deputy Police Chief Christopher Martin described the seized object as “a realistic looking fake handgun of some kind,” noting however he was “unsure if it is a BB gun or a different style of prop type gun.”

All four students were taken into custody, police said. Their identities are not being made public because they are minors.

Pratt, in his email to parents later Tuesday afternoon, said “all the students involved in this incident will be brought before the board for expulsion proceedings and some may also face criminal charges.”

School officials provided a “debriefing of the incident” for students and staff prior to them being released for the day, police said.

“I fully recognize that situations like this are extremely stressful for everyone involved. Please know I take the safety of our students and staff very seriously,” said Pratt.

In addition to the Claremont Police Department, police from Charlestown, Cornish, Newport and Plainfield responded, along with the Claremont Fire Department, Golden Cross Ambulance, New Hampshire State Police and the Sullivan County Sheriff’s Office, Martin said.

Contact John Lippman at jlippman@vnews.com.