After one Paso Robles High School student sent another an image with a handgun, authorities placed four schools on lockdown, or “shelter in place,” on Tuesday.

At about 11 a.m., a student met with Paso Robles police investigators and told them that he received a Snapchat message from another student that depicted the student holding a handgun. Law enforcement officers from six agencies then searched the Paso Robles High School campus, as well as nearby parks.

Police recommended a shelter in place order because of the specific nature of the report, a city news release states. The Paso Robles Joint Unified School District then activated the shelter in place at Paso Robles High School, Lewis Middle School, Liberty High School and Independence High School.

During the shelter in place, instruction continued in classrooms, but no one was allowed to enter or exit the campuses. Officers determined any potential threats had been mitigated, and administrators lifted the shelter in place.

An investigation into the case is ongoing. Investigators are continuing to interview students and examine evidence.