TexasCHLforum.com

I remember hearing a more detailed report about this, the story i got is the cop had a guy stopped and was working that and people milling about we're walking between the cop car and the stopped driver as they were walking around going different places. He had apparently become annoyed by that and started yelling at people to go around the cars. People would keep coming as obviously people coming into the area wouldn't necessarily have heard him. The girl was following friends, did not hear any of this, and just tried to pass through and be on her way. She was just in the wrong place when he snapped.

This was from a local news report so its value is as good as you trust the news. Seems very plausible though.