A series of threatening graffiti messages has caused Colorado’s Columbine High School to be locked down today, the Associated Press reports. Students must stay in the building all day unless they have an approved appointment.
School officials planned to have extra security officers and sheriff’s deputies on hand, and staff members will monitor doors. The Jefferson County Sheriff’s Office described the threats as a message that “harm may come to others.” The threats were written with either a marker, a pencil or a pen.
The school was the site of a shooting spree on April 20, 1999, when students Eric Harris and Dylan Klebold fatally shot 12 students, one teacher and themselves.