A couple years ago we were in DC on vacation. We walked around the WH on a nice evening. A couple of the guards were changing stations, and one was leaving the inner area to go outside onto the sidewalk and the street. He opened the inner gate, stepped into the"airlock", closed the inner gate, then opened the outer gate. As he stepped out, a lady tourist was goofing around and said, "Hold that door!" He joked, sort of, back at her and said, "Ma'am, if you go through that gate, we are going to have to rassle." I think she got the message that it wasn't a joking matter. As we walked around the back side, where Marine One lands all the time, we saw the black Suburbans driving around. The guys inside were geared up heavily, and plenty of binoculars and scopes were visible along the top of the WH. As we were walking along the path out back, a couple of Secret Service agents were quietly herding us all towards the side streets. I asked one guy about it, he just said that "something had come up". I noticed another guard smiling and nodding at us all as we walked past, he was carrying what looked like a kevlar-type briefcase with one hand inside; he was gripping some sort of short barreled rifle. They really have a large area to cover, larger than it looks on TV, and some dumbass can get over that fence faster than they can get guards out to get him. I bet they could drop someone with a shot from the roof, too, but that might not play well on the news.