"These things, unfortunately, do happen and you do have to investigate these things to the fullest extent," said Michael Kingsley, a parent.
District officials said they've been taking every precaution.
Superintendent Robert Siminski also stated in the note that the school requested state police to provide bomb-sniffing dogs to do a full sweep of the building before the start of school on Monday. There will also be a heavy state and local police presence throughout the day.
"While we are taking all of these precautions, we will understand if you decide to keep your middle school child home," Siminski said.
Officials and police have not yet determined who wrote the message.
Parents told Eyewitness News that they've been going about their normal routines. While some considered keeping their children home, they ultimately decided against it.
"She has a couple tests today," said Lisa Nolt, a parent. "She's afraid she's going to miss some important things that are going on because it's the end of the year, so she's uncomfortable, so she decided to make the decision to go."
"I have faith in the police and their investigative duties, so I would have no problem having my child here today," Kingsley said.
The incident came about two months after a similar one at both the high and middle schools. In that case, it was in the boys' bathroom.
"It's just unsettling that it keeps happening here, and it's a constant worry for me," Nolt said.
State and Hebron police said they'll be patrolling for the rest of the school day.
In the past, Siminski told Eyewitness News that the consequences for making these kinds of threats can result in expulsion and criminal charges from police.
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