The Proclamation issued by the President of the United States orders that the American flag be flown at half-staff as a mark of respect to honor Capitol Police Officers Brian D. Sicknick and Howard Liebengood, along with all Capitol Police Officers and other law enforcement personnel. This order applies to the White House, all public buildings, military posts, naval stations, and U.S. diplomatic offices both domestically and internationally, lasting until sunset on January 13, 2021. This gesture recognizes the service and sacrifice of those who guard the nation's capital and maintain order across the country.
Simple Explanation
The President asked that flags be flown lower than usual, to show respect for two special police officers and all who help keep people safe. This happened everywhere in the country until a certain day in January.