1. Massacre at Virginia Tech

Massacre at Virginia Tech

On Apr. 16, Cho Seung-Hui, a troubled Virginia Tech senior, killed 32 people before taking his own life in the deadliest school shooting in U.S. history. The episode brought many unsettling issues to the fore, including loopholes that let the mentally ill buy guns, privacy laws that restrict school counselors' ability to tell others about a distressed student and the difficulty universities have in alerting entire campuses to imminent danger. The role of the media was also scrutinized after NBC aired photos and video that Cho had mailed to the network in between killing two people in a dorm and shooting many more in classrooms.