A New Low in Police Overreaction

A University of Virginia student bought "bottled water, cookie dough and ice cream," and got approached by state Alcoholic Beverage Control in plainclothes, who thought that she was purchasing beer--apparently, the agents thought that the student was underage. One apparently pulled a gun and the student, unaware of who they were, tried to flee. They even went so far as to try to break the windows of her car when she tried to get away (wouldn't you have tried to get away if you didn't know who these people were?).

After finding out who the agents were, the student apologized, but that wasn't good enough and she was charged with three felonies and spent time in jail. Ironically enough, she apparently got arrested after calling 911 in order to report her encounter with the people who turned out to be Alcoholic Beverage Control agents. 

Here's what I'm wondering: Why were the agents in plainclothes? Why not wear uniforms to (a) identify oneself; and (b) deter underaged people who see the uniformed agents from buying beer? Here's something else I'm wondering: Will the agents be fired? I am betting the answer to that is "no," which of course would make this shocking story even more appalling.