Examining the U.S. Capitol Attack: A Review of the Security, Planning, and Response Failures on January 6 [open pdf - 2MB]
From the Executive Summary: "On January 6, 2021, the world witnessed a violent and unprecedented attack on the U.S. Capitol, the Vice President, Members of Congress, and the democratic process. Rioters, attempting to disrupt the Joint Session of Congress, broke into the Capitol building, vandalized and stole property, and ransacked offices. They attacked members of law enforcement and threatened the safety and lives of our nation's elected leaders. Tragically, seven individuals, including three law enforcement officers, ultimately lost their lives. [...] This report addresses the security, planning, and response failures of the entities directly responsible for Capitol security--USCP [United States Capitol Police] and the Capitol Police Board, which is comprised of the House and Senate Sergeants at Arms and the Architect of the Capitol as voting members, and the USCP Chief as a non-voting member--along with critical breakdowns involving several federal agencies, particularly the Federal Bureau of Investigation ('FBI'), Department of Homeland Security ('DHS'), and Department of Defense ('DOD'). The Committees also made a series of recommendations for the Capitol Police Board, USCP, federal intelligence agencies, DOD, and other Capital region law enforcement agencies to address the intelligence and security failures."
U.S. Senate Committee on Rules and Administration: https://www.rules.senate.gov/