Virginia’s colleges and universities have quietly investigated hundreds of students, employees and others in recent years to prevent a repeat of the Virginia Tech massacre of 2007, when a student gunman left a series of increasingly disturbing warning signs before killing 32 people and himself, the Associated Press reports. Monday marks the fifth anniversary of Seung-Hui Cho’s deadly rampage, the worst mass shooting in modern U.S. history. A state panel investigating the killings determined that professors, students and mental-health professionals knew about Cho’s troubled behavior for years but never tied all the information together — something officials said might have prevented the slayings. In response to the panel’s findings, the General Assembly passed a law in 2008 requiring Virginia’s 15 public, four-year colleges and universities to form panels with broad powers to investigate students’ academic, medical and criminal records. And their findings are largely exempt from public disclosure laws…