I saw this guy walking when I was on one side of the street and he was on the other. I wanted to make an image of him so I crossed the street and caught up to him on the London Bridge. I could tell he wasn't all there by the way he was dressed, which is what caught my attention to begin with. When I caught up to him, as he was standing at attention facing the street. I raised my camera to take a shot and he came after me. I have been shooting on continues focus lately and it worked out the camera tracked his movement nicely. He was not threat to me, I stood my ground till he backed off and I went on my way.