New footage of the January 6 riots at the US Capitol shows House speaker Nancy Pelosi calmly trying to take charge of the situation as she sheltered at Fort McNair, two miles south of the Capitol.

“There has to be some way,” she told colleagues, “we can maintain the sense that people have that there is some security or some confidence that government can function and that you can elect the president of the United States.”

Then an unidentified voice interjected with alarming news: lawmakers on the House floor had begun putting on teargas masks in preparation for a breach. Pelosi asked the woman to repeat what she said.

“Do you believe this?” Pelosi said to another Democratic leader, Jim Clyburn of South Carolina.

The footage was from about 2.45pm, when rioters had already disrupted the planned certification of the 2020 presidential election results. It would be hours before the building was secure.

Never-before-seen video footage played Thursday by the House of Representatives select committee investigating last year’s riot shows how Pelosi and other leaders, including Republican allies of Donald Trump, responded to the insurrection.

The recordings offer a rare glimpse into the real-time reactions of the most powerful members of Congress as they scrambled to drum up support from all parts of the government, including from agencies seemingly ill prepared for the chaos, and vented anger over a president whose conduct they felt had endangered their lives.

In the videos, Pelosi and Senate majority leader Chuck Schumer negotiate with governors and defence officials to try to get the national guard to the Capitol as police were being brutally beaten outside the building.

The deployment of the guard was delayed for hours as Trump stood by and did little to stop the violence of his supporters.

The footage, recorded by Pelosi’s daughter, Alexandra, a documentary film-maker, was shown during the committee’s 10th hearing as an illustration of the president’s inaction in the face of the grave danger posed by the rioters.

“As the president watched the bloody attack unfold on Fox News from his dining room, members of Congress and other government officials stepped into the gigantic leadership void created by the president’s chilling and steady passivity that day,” said Democratic congressman Jamie Raskin, a committee member.

The concerns were not theoretical. At roughly 3pm, as a Trump loyalist outside Pelosi’s office pointed her finger and shouted, “Bring her out now!” and, “We’re coming in if you don’t bring her out!” the speaker was in a room with Schumer, who said: “I’m gonna call up the effin’ secretary of DoD.”

As the violence persisted at the Capitol – “Officer down, get him up,” a voice could be heard bellowing in one clip shown by the committee – the leaders kept making calls from Fort McNair. One went to Virginia governor Ralph Northam about the possibility of help from the Virginia national guard, with Pelosi narrating the events based on what she saw from television news footage.

An angrier call followed with Jeffrey Rosen, the then acting attorney general. Days earlier, and unbeknownst at the time to Congress or to the public, Rosen and colleagues had fended off a slapdash attempt by Trump to replace him with a subordinate eager to challenge the election results.

On that day, though, Schumer and Pelosi sat shoulder-to-shoulder on the couch and laid bare their frustrations with the country’s top law enforcement official.

Throughout the footage, Pelosi maintains her composure, barely raising her voice as she urges Rosen, and later vice-president Mike Pence and others, to send help and tries to work out a way for the House and Senate to reconvene.

“They’re breaking the law in many different ways,” Pelosi said to Rosen. “And quite frankly, much of it at the instigation of the president of the United States.”

Schumer weighed in too: “Yeah, why don’t you get the president to tell them to leave the Capitol, Mr attorney-general, in your law enforcement responsibility? A public statement they should all leave.”

It wasn’t until the evening that the Capitol would be cleared and work would resume. The news that Congress would be able to reconvene to finish its work in certifying the election results was delivered to the congressional leaders not by Trump but by Pence.

The House January 6 committee voted unanimously Thursday to subpoena Trump, demanding his personal testimony as it unveiled startling new video of close aides describing his multi-part plan to overturn his 2020 election loss that led to his supporters assault on the Capitol.