A gunman was on the loose on Thursday at Virginia Tech after he shot a police officer and possibly a second person, said the university, scene of a 2007 massacre in which 32 people died. “Suspect remains at large. A police officer has been shot. A potential second victim is reported at the Cage lot. Stay indoors. Secure in place,” it told students and staff on its website (www.vt.edu). Collegiate Times, a student newspaper, said on its Twitter account that one person had been killed. It also tweeted a photograph of a parking lot with what appeared to be a shrouded body on the ground, surrounded by police tape.