Three students in Prince William County were charged after making threats to two different schools in the county.

In one threat, two students are accused of threatening a teacher over the social media app Snapchat. In another threat, an 11-year-old student is accused of writing a note on a bathroom stall, threatening to bomb the school.

On Monday morning, in the first incident, police said a school resource officer received a tip that two students sent messages over Snapchat suggesting violence against a specific teacher at Patriot High School in Nokesville, Va.

The students also posted a picture of a suspected firearm, which ended up being a BB gun. The officer found and talked with the students and determined the threat was not credible, Prince William County Police said.

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The students—a 16-year-old boy from Bristow and a 14-year-old boy from Gainesville—are both charged with threats of serious bodily injury on school property.

They were released to the custody of a family member.

Also on Monday there was a second incident Covington-Harper Elementary School in Dumfries, Va. where police say a school staffer reported seeing a bomb threat written on a bathroom stall around 1:50 p.m.

All student and faculty were evacuated from the building. After a search of the building and surrounding area, police said the threat was not credible.

An 11-year-old male student was charged with knowingly communicating a false threat to bomb.