One day after thousands of President Trump’s supporters besieged the U.S. Capitol, questions were still being asked about how a federal building in the most policed city in America could have been overtaken so easily.

The U.S. Capitol Police broke its silence nearly a full day after the attack began, saying Thursday that its officers acted “valiantly,” but lawmakers, congressional staff, and media who were trapped inside federal buildings on Capitol Hill were still confused over how the building was breached and wanted to know who was ultimately responsible for letting it happen.