Explained: How security failures enabled Trump mob to storm US Capitol

The bloody chaos inside the US Capitol came after the police force that protects the legislative complex was overrun by a mob of Trump supporters in what law enforcement officials called a catastrophic failure to prepare.
 
While events such as a presidential inauguration involve detailed security plans by numerous security agencies, far less planning went into protecting the joint session of Congress that convened on Wednesday to ratify the results of the presidential election, the officials said. That lapse came despite glaring warning signs of potential violence by hardline supporters of President Trump, who are inflamed by Trump’s baseless claims of a stolen election and hope to block the inauguration of President-elect Joe Biden.
 
And security initially was handled almost entirely alone by the US Capitol Police, a 2,000-member force under the control of Congress. For reasons that remained unclear as of early Thursday, other arms of the US federal government’s vast security apparatus did not arrive in force for hours as rioters besieged the seat of Congress. Despite those rumblings of danger, the Capitol Police force did not request advance help to secure the building from other federal agencies such as the Department of Homeland Security, according to one senior official. The Capitol Police did not respond to requests for comment.
 
Lawmakers inside the building blamed a lack of preparation for the historic security breach. Some Democratic members of Congress, worried about the prospects of violence, tried for more than a week to press agencies for information about what they knew about threats or countermeasures, according to one congressional source. But there was no sign anyone was gathering serious intelligence about possible disturbances or planning to counter them. Trump on Twitter promised a “wild” event aimed at reversing his loss in last November’s election — and appeared to encourage his supporters to act.