A Maryland teenager has been charged with making a series of violent threats against Towson High School that have disrupted classes and rattled students, staff and their families despite assurances from school officials and police that the threats were unsubstantiated.

The Baltimore County Police Department announced Saturday that the charges stem from an investigation led by Towson detectives and that additional charges are pending against a second adolescent in North Carolina.

Investigators believe the two suspects intended to incriminate a third, uninvolved Maryland adolescent in their plot to stoke fear about attacks on the school. The nature of the relationship between the two suspects and their motive for trying to pin the plot on another teen are still under investigation, police spokesperson Joy Stewart said.

“Parents can feel comfortable sending their children to school on Monday as a result of these charges,” Stewart said in an interview. “And there’s still no reason to believe that any of these threats could have been carried out.”

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The first threat was made last month, when some members of the school community received a message threatening a mass shooting. Two weeks later, the high school received another threatening email alleging that explosives had been placed in the building. Both times, extra police officers were sent to the school, even though the threats were not considered credible.

In a statement, county police thanked the Towson High School community “for their patience and support during this investigation.”

Baltimore County Executive Johnny Olszewski said in a statement that he’s proud of the county police for “getting to the bottom of the concerning situation at Towson High School.”

“Any threat of violence is reprehensible, especially when targeted at a school community,” he said. “Baltimore County will not tolerate these threats and has demonstrated that we will do whatever is necessary to ensure the safety and well-being of our children and educators.”

Towson is not the only area school that has been impacted this school year by scary, anonymous threats. The Howard County Public School System has received four such threats, a spokesperson said, and across the country, nearly 200 schools in 28 states have received false threats connected to a single person living overseas, NPR found.