Like to take pictures? Well you may have run afoul of shooting photos of federal buildings (which is pretty easy to do in DC where I live). Here's a useful federal directive that you should print out and put in your camera bag.
Federal Protective Service Information Bulletin of Aug. 2, 2010, emphasizing "the public's right to photograph the exterior of federal facilities" from "publicly accessible spaces such as streets, sidewalks, parks and plazas." It also states that in a field interview, "officers should not seize the camera or its contents, and must be cautious not to give such 'orders' to a photographer to erase the contents of a camera."
Download it here – http://documents.nytimes.com/photographing-federal-buildings-from-public-spaces