Weird Heckler

I've had some passersby make some odd (or sometimes, inappropriate) comments before--after all, this is a large city with its share of strange people--but this latest incident takes the cake. I was crossing the street from the train station, and a guy on a bike, wearing some type of uniform, road past. He looked directly at me, grinned, and said, in a loud voice, "DING DING DING DING DING!!!"