There are racists here and they are out in force.
http://www.nytimes.com/2012/03/19/us/911-tapes-released-in-killing-of-florida-teenager.html?_r=1
There are several recordings of the several 911 calls made that night by residents. Bottom left of the page at link.
The third recording has the title “There’s just someone screaming outside.”
In this recording you hear screaming and then a gunshot.
Bearing in mind that there are two people in an altercation; one has a gun and the other has a can of iced tea and a bag of Skittles...
Listen to that recording and ask yourself which one is screaming like that.