The ROTC cadets getting ready to leave their class at Old Dominion University in Virginia last month had never seen the stranger who entered the room, and they thought maybe he was someone early for the next class. But he seemed nervous when he asked whether it was an ROTC class. “I wasn’t thinking about what that question really meant,” Louis Ancheta said. Then the man reached into his waist, pulled out a Glock handgun and shouted something — some heard it as “Allahu Akbar” — and began firing,