From the GAO report:
Over the course of about 7 hours, more than 2,000 protesters entered the U.S. Capitol on January 6, disrupting the peaceful transfer of power and threatening the safety of the Vice President and
members of Congress.
The attack resulted in assaults on at least 174 police officers, including 114 Capitol Police and 60 D.C. Metropolitan Police Department officers.
These events led to at least seven deaths and caused about $2.7 billion in estimated costs.
The footnote on the cost estimate reads:
This amount reflects, among other things, damage to the Capitol building and grounds, estimated costs borne by the Capitol Police, the District of Columbia, and federal agencies, and estimated costs to address security needs and investigations as described in budget and funding requests, appropriations, agency estimates, and other publicly available information.
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https://www.gao.gov/assets/d23106625.pdf
