Following the shootings, Virginia Tech began employing an alert system on their website and text messages to warn students of danger. The alert system was first activated in 2008 when an exploded cartridge from a nail gun produced sounds similar to gunfire near a campus dormitory. It was again activated on August 4, 2011, when children attending a summer class reported a man carrying a handgun; police were unable to find anyone matching the children's description. Later in 2011, on December 8, the system was activated again after a police officer was shot and killed on campus. This turned out to be a random act by a part-time Radford University student who had carjacked a Mercedes SUV earlier in the day in nearby Radford and had parked it in the general area of a Virginia Tech parking lot, where the officer was conducting a routine traffic stop on a third party. The shooter turned the gun on himself a half-hour later.