A phone call to Baltimore-area police led to the arrest of an 18-year-old Montgomery County high school student. The student is charged with threats of mass violence, and authorities said it took several agencies working together to make the arrest, including the FBI. In a joint investigation with the FBI, Montgomery County police said they discovered a manifesto written by Andrea Ye, 18, of Rockville, whose preferred name is Alex Ye. Authorities said the writing was about committing mass shootings at two Rockville schools: Wootton High School, which Ye had attended online, and Lakewood Elementary School, which Ye attended.