Virginia Tech campus is on lockdown Thursday after police received reports of a gunman sighting. Three children attending summer camp reported seeing a man holding a gun concealed by a cloth, walking quickly toward the volleyball courts. The university issued an alert on its website at 9:37 a.m. asking students and faculty to remain inside and secure doors. In 2007, Virginia Tech saw the deadliest mass shooting in modern U.S. history when a gunman shot and killed 33 people.