WASHINGTON (AP) — A violent mob loyal to President Donald Trump stormed the U.S. Capitol on Wednesday and forced lawmakers into hiding, in a stunning attempt to overturn America’s presidential election, undercut the nation’s democracy and keep Democrat Joe Biden from replacing Trump in the White House.

The nation’s elected representatives scrambled to crouch under desks and don gas marks, while police futilely tried to barricade the building, one of the most jarring scenes ever to unfold in a seat of American political power. A woman was shot and killed inside the Capitol, and Washington’s mayor instituted an evening curfew in an attempt to contain the violence.

The rioters were egged on by Trump, who has spent weeks falsely attacking the integrity of the election and had urged his supporters to descend on Washington Wednesday to protest Congress’ formal approval of Biden’s victory. Some Republican lawmakers were in the midst of raising objections to the results on his behalf when the proceedings were abruptly halted by the mob.

Together, the protests and the GOP election objections amounted to an almost unthinkable challenge to American democracy and exposed the depths of the divisions that have coursed through the country during Trump’s four years in office. Though the efforts to block Biden from being sworn in on Jan. 20 were sure to fail, the support Trump has received for his efforts to overturn the election results have badly strained the nation’s democratic guardrails.

House Speaker Nancy Pelosi said lawmakers were resuming the counting of electoral votes Wednesday evening after the Capitol was cleared of the pro-Trump occupiers.

The president gave his supporters an added boost Wednesday morning during an appearance at a rally outside the White House, where he urged them to march to the Capitol. He spent much of the afternoon in his private dining room off the Oval Office watching scenes of the violence on television. At the urging of his staff, he reluctantly issued a pair of tweets and a taped video telling his supporters it was time to “go home in peace” — yet he still said he backed their cause.

Hours later, Twitter for the first time time locked Trump’s account, demanded that he remove tweets excusing violence and threatened “permanent suspension.”

A somber President-elect Biden, two weeks away from being inaugurated, said American democracy was “under unprecedented assault,” a sentiment echoed by many in Congress, including some Republicans. Former President George W. Bush said he watched the events in “disbelief and dismay.”

“What happened here today was an insurrection, incited by the President of the United States,” said Republican Sen. Mitt Romney of Utah.

There were harsh words from major business organizations and the Republican National Committee, too, suggesting uneasy relations with Trump were skidding into divorce as he leaves Washington.

“Our soldiers have died carrying the American flag into battle for our freedom,” tweeted RNC communications director Michael Ahrens. “To see that flag used in the name of unfounded conspiracy theories is a disgrace to the nation, and every decent American should be disgusted by it.”

Trump, unrepentant, had tweeted, “These are the things and events that happen when a sacred landslide election victory is so unceremoniously & viciously stripped away from great patriots who have been badly & unfairly treated for so long.”

“Remember this day forever!”

The domed Capitol building has for centuries been the scene of protests and occasional violence, including a 1954 shooting involving Puerto Rican nationalists. But Wednesday’s events were particularly astounding both because they unfolded at least initially with the implicit blessing of the president and because of the underlying goal of overturning the results of a free and fair presidential election.