From the Prince William police press release:
Threats on School Grounds – On March 7 at 4:27PM, officers received information of a potential threat of violence at Rippon Middle School located at 15101 Blackburn Rd in Woodbridge (22191). The investigation revealed that a student, a 14-year-old male, communicated over the social media app “Snapchat” suggesting an act of violence at the school. A search warrant was subsequently executed at the residence of the student. Following the investigation, officers obtained a petition for the student who was served and released back to the custody of a family member.