Virginia Tech, site of a 2007 mass shooting, issued a campus lockdown Thursday after a man with a gun was reportedly spotted on campus. NBC affiliate WSLS confirmed that the campus siren system had been activated and all people on campus had been asked to remain indoors. The university issued an alert on its website at 9:37 a.m. Thursday telling students and employees to stay inside and secure doors. A subsequent crime alert said three children attending a camp on campus reported seeing a white man who appeared to have a gun covered with a cloth.