Some were locked in. Some were locked out. But everyone with business in the Cannon House Office Building on Thursday had to wait.

Here staffers mill about inside the Rotunda as a window reflects others who were not allowed into the building. Capitol Police guarded the doors as officers searched the building for what they thought was a man who had run from a security checkpoint with a gun in his bag. The nearly two-hour incident turned out to be a false alarm: After police revised their description of the alleged perpetrator, two female staffers came forward saying they had carried a toy gun through the checkpoint as part of a Halloween costume.