Taking advantage of a mostly vacant campus, Clemson University officials teamed up with local emergency responders to host an “active threat” drill over fall break. It started with an emergency alert through the school’s email and texting notification system, and included actors posing as victims and perpetrators in the area around Tillman Hall. With active shooter incidents still a recent memory for some colleges, it’s an unfortunate necessity for Greg Mullen, the university’s police chief. Months of effort went into planning the full-scale exercise, which included three university departments, seven law enforcement agencies, five EMS agencies and hospitals, two dispatch centers, two emergency management agencies and six other campus partners.