Yesterday around 12:30PM I was walking down a narrow street in Brooklyn (61st Street, between 8th and 9th Avenue) and there was a man wearing a red tshirt walking really slowly in front of me and taking up the entire sidewalk. I was in a rush so I walked faster, hoping to get ahead of him. When I quickened my pace, he started walking faster as well (I was wearing flip flops so he could hear me walking faster) which I thought was a little odd. I kept walking faster, and he kept walking faster, but I ultimately got in front of him, but I could still hear him walking really fast behind me to try and catch up which made me feel slightly nervous. I felt a poke from behind and I turned around and the sick perv had his penis hanging out. Now that he had my attention he resumed his slow pace. I was too shocked/disgusted/angered to say or do anything so I just crossed the street and walked in the opposite direction.