Prince George's County Police arrested a Parkdale High School student in connection with a threat of violence at the school.
The student set up a clown-themed Twitter account while in class and used it to threaten to harm anyone at the school in Riverdale, Maryland, Monday. He is charged with threat of mass violence.
Investigators also identified a student who made a bomb threat to Bladensburg High School, police said. The threat does not appear to be credible.
Police continue to investigate that threat, and the school is disciplining the student.
"While perpetrators may believe certain apps provide anonymity, these investigations show otherwise," Police Chief Hank Stawinski said.
Similar threats to other schools are also under investigation, police said.
Police maintained higher than normal visibility at several public schools Monday in response to the unsubstantiated threats.
"We will have additional officers at schools out of an abundance of caution. We take these threats seriously," the police department tweeted on Sunday.
All public schools were open Monday as scheduled.
WTOP reports that Elizabeth Seton High School, a private school near Bladensburg High School, was closed Monday out of an abundance of caution due to the threat.
Mysterious sightings of creepy clowns have been reported across the country in recent weeks.