Wrong Block?

I was outside watering my garden yesterday when I heard a voice say:
"You don't need to be here, You're on the wrong block! Thats right, I'm talking to you. You ugly white f--k!"
I think I would have felt intimidated by this, but the shouting came from a very innocent looking 9yr old girl who was walking home from school with her friends. How can I respond to this? My roommate later pointed out that this girl might have been addressing his girlfriend who was sitting on my front porch with him, but it doesn't make much sense that someone would just randomly deride a person on my porch for being female and white. No one ever said things like this to me in Minnesota. I am really confused and a little bit scared because I can't imagine that a 9 yr old girl came up with such things by herself.