The chairman of the House select committee investigating the deadly January 6 assault on the US Capitol in 2021 said Donald Trump was at the center of a sprawling conspiracy to overturn the results of the presidential election that culminated in an “attempted coup”.

Congressman Bennie Thompson, a Democrat of Mississippi, describing the grave threat posed to American democracy then and now by the former president’s actions, during an extraordinary public hearing in Washington on Thursday.

Thompson, the committee’s chair, and congresswoman Liz Cheney, a Republican of Wyoming and its vice-chair, laid out what they described as the “unconstitutional” misconduct of a former president who continues to peddle the lie that the election he lost to Democrat Joe Biden was stolen from him.

“All Americans should keep in mind this fact,” Cheney said during the primetime proceedings, “on the morning of January 6, President Donald Trump’s intention was to remain president of the United States despite the lawful outcome of the 2020 election and in violation of his constitutional obligation to relinquish power.”

Their presentation featured never-before-seen footage from the attack by extremist supporters of Trump who broke into the US Capitol to try to stop Congress certifying Biden’s win.

And they weaved the film of the violence together with live testimony and videotaped depositions behind closed doors of Trump’s closest allies and family members.

These included the former attorney general, William Barr, Donald Trump’s daughter and White House adviser, Ivanka Trump, his son-in-law and adviser, Jared Kushner, and a longtime aide and spokesman, Jason Miller. The effect was cinematic and piercing.

The opening act of what will be a series of six public hearings by the committee was full of revelations.

Members of the audience gasped when Cheney said that, after being informed the mob was calling for his vice-president, Mike Pence, to be hanged, Trump told aides that perhaps he “deserved” it.

The committee showed a clip of the then US attorney general, Bill Barr, saying he “repeatedly” told Trump “in no uncertain terms” that he had lost the election and the claims of it being “stolen” because of widespread voting fraud in key states were “bullshit”.

In another interview, Ivanka Trump said she “accepted” Barr’s determination that the presidential election, won by Democrat Joe Biden, had been fair.

Cheney also announced that multiple House Republicans had sought pardons from Trump for their involvement in the January 6 riot, including congressman Scott Perry of Pennsylvania, who has refused a request to testify before the committee.

The evening presentation also included eyewitness testimony from Nick Quested, a British documentary film-maker who was embedded with the far right extremist Proud Boys group that led the storming of the Capitol.

And from Caroline Edwards, a Capitol police officer who described in harrowing detail how she was assaulted when the mob descended on the building. She said she was knocked unconscious on the steps and after she came to, she ran to help overwhelmed officers trying to stop insurrectionists breaking into the Senate.

The scene was like a “war zone” she said, and she was slipping on her fellow officers’ blood. “It was carnage. It was chaos,” she said.

Drawing on the findings of their nearly year-long investigation, which includes more than 100 subpoenas, 1,000 interviews and 100,000 documents, the select committee will attempt to establish a comprehensive sequence of events that built to the cold January day when Trump urged supporters to “fight like hell” to protect his presidency.

The attack, which played out in real-time on national television, left more than 100 police officers injured, as they clashed with a pro-Trump mob, some armed with bats, clubs and bear spray. Nine people lost their lives in connection with the riot, including a woman who was ​​fatally shot by a Capitol police officer as she attempted to breach the House chamber.

Convincing a deeply polarized American public that the Capitol riot was not a spontaneous act of violence but the culmination of a months-long plot by Trump and his allies to undermine the results of a free and fair election is no easy task for the committee.

Thompson argued that American democracy “remains in danger” as many Republicans at local and national level continue to boost the myth that the 2020 election was stolen from Trump and use it in their own election campaigns.

“The conspiracy to thwart the will of the people is not over,” Thompson said..

“January 6th and the lies that led to insurrection have put two and a half centuries of constitutional democracy at risk,” he added. “The world is watching what we do here.”

The select committee is composed of seven Democrats and two Republicans.

Speaking from the Summit of the Americas in Los Angeles before the hearing on Wednesday, Biden said the assault on the Capitol was a “clear and flagrant violation of the constitution”.

“A lot of Americans are going to see for the first time some of the details,” he said.

Meanwhile, an unrepentant Trump, who was banned from Twitter following the January 6 assault, posted on his own Truth Social social media platform, calling the forces unleashed in the attack on the Capitol not an insurrection or a deadly riot, but a movement.

“January 6th was not simply a protest, it represented the greatest movement in the history of our country to Make America Great Again,” Trump said.

Hundreds have been charged in connection with the events of January 6, and some have even been charged with seditious conspiracy, including the leader of the Proud Boys, Enrique Tarrio. The committee showed several clips of the defendants saying the reason they came to Washington on January 6 was because Trump told them to.

The hearings will resume next week.

“We’re going to take a close look at the first part of Trump’s attack on the rule of law,” Thompson said, “when he lit the fuse that ultimately resulted in the violence of January 6th.”