Harlem woman

I meant to post this snapshot last week. I'm really happy with it. I took this picture with my point & shoot camera just after my wife and I emerged from the 125th street subway station in Harlem. I like the well put together woman who is out and about on a sunny Sunday morning. I know the back story behind this image but when I look at it as a fresh observer I enjoy the mystery. What are the police doing? Why the expression on her face?