WALES, Maine (NEWS CENTER) -- Since Monday, RSU 4, which encompasses Litchfield, Sabattus, and Wales, has had three bomb threats.
The first, at Oak Hill Middle School, was exactly one week after the Boston Marathon bombings.
The second happened the next day, at Oak Hill High School.
The latest was Thursday afternoon, at the Carrie Ricker Elementary School.
According to RSU Superintendent Jim Hodkin, all three threats were written in school bathrooms.
"Kids are frustrated with it, and they feel unsafe," said Superintendent Hodkin.
He added that three weeks ago, just before April vacation, there had been another bomb threat within the school district.
"These things go in cycles, and rarely ever is it one incident and then it's done," said Hodkin.
He said the district has been following evacuation plans put in place, and working with local law enforcement to apprehend the suspects.
It has given him the chance to re-examine evacuation procedures. He explained that when a threat comes in to the middle school, students are evacuated to the high school, and vice versa.
Someone mentioned to him that if someone wanted to harm students, they would simply threaten one school, and target the evacuation destination.
"Schools should go through the process of reviewing their response plans on a regular basis, particularly, unfortunately, in the world we live in now," said Hodkin.
He said the threats are being treated as criminal investigations, and with the help of local law enforcement, they have identified their suspect in the middle school bombing threat as a student from that school.