The Justice Department accused a man of unlawful entry and assaulting a police officer in the first criminal charges to emerge from the siege of the U.S. Capitol by a mob egged on by President Donald Trump. Mark Leffingwell was charged Thursday in federal court in Washington. According to a statement of facts filed alongside the complaint, he attacked an officer at the scene. Leffingwell "attempted to push past me and other officers," Capitol Police Officer Daniel Amendola said in the statement. "When he was deterred from advancing further into the building, Leffingwell punched me repeatedly with a closed fist. I was struck in the helmet that I was wearing and in the chest." According to the statement, Leffingwell later "spontaneously apologized" for striking the officer. The violent mob stormed the Capitol on Wednesday afternoon, charging past police barriers, smashing windows and sending lawmakers fleeing for safety. The riot, which resulted in four deaths, forced members of Congress to temporarily abandon their formal certification of President-elect Joe Biden's victory in the November election. The lawmakers returned and completed the certification once the building was secured. "Yesterday, our nation watched in disbelief as a mob breached the Capitol Building and required federal and local law enforcement to help restore order," acting Attorney General Jeffrey Rosen said Thursday. "The Department of Justice is committed to ensuring that those responsible for this attack on our government and the rule of law face the full consequences of their actions under the law." Photos and videos of rioters brawling with police and ransacking lawmakers' officers were widely circulated on social media Wednesday afternoon. Legal experts say a wide variety of crimes—everything from vandalism to sedition—occurred during the riot and that prosecutors could charge offenders even if they walked away from the incident without being detained. Participants could be charged with the "willful injury of federal property," as well as assaulting law enforcement officers and trespassing, legal experts said. Some could also face more serious charges, including sedition and insurrection, which would require proving an intent to disrupt or even overthrow the government. Shortly after lawmakers certified the election results early Thursday, Trump said in a statement there would be an "orderly transition" of power to Biden on Jan. 20, noting that he continued to "disagree with the outcome of the election." Text by David Yaffe-Bellany and Chris Dolmetsch / Bloomberg