Sight of off-duty cop's holster triggers lockdown at D.C. university WASHINGTON, Dec. 12 (UPI) -- The reported gunman who triggered a two-hour lockdown at American University in Washington was an off-duty police officer, officials say. The lockdown was instituted after a student reported seeing a man on a campus bus wearing what he thought was a holster, CNN reported Thursday. The report triggered the campus to send out a mass email alert about 8 p.m. Wednesday warning: "Man with gun seen on campus. Campus is on lockdown. Shelter in place. The man with the holster turned out to be a off-duty officer with the D.C. police department, Lt. Jesse Porter said. He was sitting next to a student he knew. University and district police posted messages on Twitter about 9:20 p.m. that the lockdown was lifted and no students were injured. "Given the culture we are in now," Porter said, police considered it advisable to respond on a massive scale. In this time and age, people get concerned.