That was the Senate Chamber.
Now if the rioters had tried to enter the House Chamber, they likely would have been shot just like Babbitt was when trying to get into the Speaker's Lobby.
2021 storming of the United States Capitol - Wikipedia
"With building security breached, Capitol Police evacuated the
Senate and
House of Representatives chambers. Several buildings in the
Capitol complex were evacuated, and all were locked down.
[49] Rioters occupied and ransacked the empty Senate chamber while federal law enforcement officers drew handguns to defend the evacuated House floor.
[50][51] Pipe bombs were found at the offices of the
Democratic National Committee and the
Republican National Committee, and
Molotov cocktails were discovered in a vehicle near the Capitol."
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