Federal prosecutors alleged in court filings unsealed afterward that Mr. Klein, 42, used a riot shield to strike police officers defending the Capitol building from the mobs as Congress met inside. Mr. Klein held a “Schedule C” politically appointed position at the State Department, as well a top-secret security clearance, at the time the Capitol was stormed by supporters of former President Trump. He resigned several days later on the eve of President Biden succeeding Mr. Trump as a result of winning November’s election, for which Congress was meeting to make official when the Capitol was stormed. “Despite his oath to support and defend the Constitution, Klein demonstrated his contempt for that oath, the legitimate functions of the government and for the Constitution itself when he assaulted officers in an attempt to stop the certification of a lawful election,” acting U.S. Attorney Channing D. Phillips argued in a court filing entered in support of keeping the defendant in custody.