WASHINGTON – Four Montgomery County 13-year-olds have been charged with juvenile offenses for making threats of mass violence against students at several county middle schools  – the latest in a series of threats against area schools this week.

The boys’ arrests come just days after two Prince George’s County students were arrested on similar charges for making threats against schools in the neighboring county. A D.C. girl was also arrested this week for calling in a bomb threat against a charter school in Northeast D.C.

Montgomery County police said that the boys made the threats to multiple students who attend Rosa Parks Middle School in a series of posts on social media. The account name included the word “clown” and the posts included photos of clowns, similar to clown-themed threats made in Prince George’s County. The posts also included pictures of axes and shovels.

A post on Instagram warned the school to “be ready” and said the attacker would come to the school on Wednesday. The posts also mentioned Argyle and Farquhar middle schools, however no specific students were named from those schools.

One of the Rosa Parks students who received a threat asked what the poster planned for the school. The response: “Kill them,” police said.

The threatened students, their parents, plus school administrators helped police investigate the threats, which led to the four boys.

The boys were arrested on Wednesday and returned to their parents’ custody. Their cases will be handled by the Department of Juvenile Services.

Police learned of the posts on Monday, the same day the first Prince George’s County student was arrested. Police in that county sent  extra officers to several schools on Monday because of the threats that cropped up last weekend.

An email sent Tuesday to parents, and obtained by WTOP, did not specify which schools had been mentioned in the threats. The note said that the postings posed no true threat to students’ safety.