Odd TSA-Like Bag Check on DC Metro

An EPJ reader emails:

Heads-up on unusual bag search if boarding at Braddock. Must allow search of your bag or you cannot carry it onto the metro. The officer claimed it was a normal random check-point and that these are conducted sporadically. He also said that they were only searching for bomb components. However, I observed a man carrying bottled water to the officers who had FBI on his jacket, clearly not metro transit cop. At least 20 officers were milling around and at least one dog.