I have photographed all sorts of buildings including those occupied by the government. People driving by have called in and reported suspicious activity. When the police show up, I am respectful and answer all their questions. They have never told me to stop. I usually thank them for doing their job and say I understand why you stopped. If some one other then an official stop me I'm also respectful. only once was I told I can't take a photo, I told him to call the police and report my activity and then went back to what I was doing without incident.