From the Washington City Paper:
According to an eyewitness, a D.C. Police detective (pictured above with gun) went nuts after kids pelted his Hummer with snowballs at 14th and U Streets NW over the weekend. The veteran detective got out of his car and eventually grabbed for his gun, displaying it to the crowd. He did not immediately identify himself as a police officer. He calmed down once his fellow uniformed cop arrived. Apparently, someone called 911 to report a man with gun. The snowball fight had been well hyped on Twitter.