SCOTTSDALE, AZ (3TV/CBS 5) – An 11-year-old boy has been arrested after a loaded gun was found in a Scottsdale middle school on Thursday. The incident began around 11:30 a.m. at Mountainside Middle School, located near 128th Street and Via Linda. That’s when a student told a staff member about a handgun on a classroom floor. A school resource officer confirmed it was real and loaded, and the school was locked down as a precaution, which lasted about three hours.