WASHINGTON (AP) — The violent siege of the Capitol by President Donald Trump’s supporters forced painful new questions across government Thursday — about his fitness to remain in office for two more weeks, the ability of the police to secure the complex and the future of the Republican Party in a post-Trump era.

The rampage that shocked the world and left the country on edge forced the resignations of three top Capitol security officials over the failure to stop the breach. It led lawmakers to demand a review of operations and an FBI briefing over what they called a “terrorist attack.” And it is prompting a broader reckoning over Trump’s tenure in office and what comes next for a torn nation.

House Speaker Nancy Pelosi said any remaining day with the president in power could be “a horror show for America.” Likewise, Senate Democratic leader Chuck Schumer said the attack on the Capitol was “an insurrection against the United States, incited by the president," and Trump must not stay in office “one day” longer.

Pelosi and Schumer called for invoking the 25th Amendment to the Constitution to force Trump from office before President-elect Joe Biden is inaugurated on Jan. 20. Schumer said he and Pelosi tried to call Vice President Mike Pence early Thursday to discuss that option but were unable to connect with him.

At least one Republican lawmaker joined the effort. The procedure allows for the vice president and a majority of the Cabinet to declare the president unfit for office. The vice president then becomes acting president.

Pelosi said if the president’s Cabinet does not swiftly act, the House may proceed to impeach Trump.

Meanwhile, other Republicans who echoed Trump’s false claims of a fraudulent election, including rising stars and some party leaders, faced angry, unsettled peers — but also those cheering them on.

With tensions high, the Capitol shuttered and lawmakers not scheduled to return until the inauguration, an uneasy feeling of stalemate settled over a main seat of national power as Trump remained holed up at the White House.

The social media giant Facebook banned the president from its platform and Instagram for the duration of Trump's final days in office, if not indefinitely, citing his intent to stoke unrest. Twitter had silenced him the day before.

Facebook founder Mark Zuckerberg said “the shocking events of the last 24 hours" make it clear Trump “intends to use his remaining time in office to undermine the peaceful and lawful transition of power.”

U.S. Capitol Police Chief Steven Sund, under pressure from Schumer, Pelosi and other congressional leaders, was forced to resign. Senate Majority Leader Mitch McConnell asked for and received the resignation of the Sergeant at Arms of the Senate, Michael Stenger, effective immediately. Paul Irving, the longtime Sergeant at Arms of the House, also resigned.

Sund had defended his department’s response to the storming of the Capitol, saying officers had “acted valiantly when faced with thousands of individuals involved in violent riotous actions.”

In his first public comment on the mayhem, Sund said in a statement earlier Thursday that rioters attacked Capitol police and other law enforcement officers with metal pipes, discharged chemical irritants and “took up other weapons against our officers.”

It was “unlike any I have ever experienced in my 30 years in law enforcement here in Washington, D.C.," said Sund, a former city police officer.

Washington Mayor Muriel Bowser called the police response “a failure.”

Lawmakers from both parties pledged to investigate and questioned whether a lack of preparedness allowed a mob to occupy and vandalize the building. The Pentagon and Justice Department had been rebuffed when they offered assistance.

Black lawmakers, in particular, noted the way the mostly white Trump supporters were treated.

Protesters were urged by Trump during a rally near the White House earlier Wednesday to head to Capitol Hill, where lawmakers were scheduled to confirm Biden's presidential victory. The mob swiftly broke through police barriers, smashed windows and paraded through the halls, sending lawmakers into hiding.

The protesters ransacked the place, taking over the House area and Senate chamber and waving Trump, American and Confederate flags. Outside, they scaled the walls and balconies.

Newly elected Rep. Cori Bush, D-Mo., said if “we, as Black people did the same things that happened ... the reaction would have been different, we would have been laid out on the ground."

One protester, a white woman, was shot to death by Capitol Police, and there were dozens of arrests. Three other people died after “medical emergencies” related to the breach.

Rep. Val Demings, D-Fla., a former police chief, said it was “painfully obvious” that Capitol police “were not prepared.”

Rep. Tim Ryan, D-Ohio, who is the chairman of a subcommittee that oversees the Capitol police budget, announced the new review and suggested there would be leadership changes on the force.

“This is an embarrassment," he said.

After the chaos, lawmakers resolved to return from shelter to show the country, and the world, of the nation’s enduring commitment to uphold the will of the voters and the peaceful transfer of power.

Vice President Mike Pence, presiding over the joint session, announced the tally, 306-232, that confirmed Biden as the presidential election winner before dawn Thursday.

Trump, who had repeatedly refused to concede the election, said in a statement immediately after the vote that there will be an “orderly transition” on Inauguration Day.

Several lawmakers suggested that Trump be prosecuted for a crime, impeached for a second time or even removed under the Constitution’s 25th Amendment, which seemed unlikely two weeks from when his term expires. The House impeached Trump in 2019 and the Senate acquitted him in 2020.

While Democrats led the charge to invoke the 25th Amendment, similar conversations among Republicans within the administration had made their way to Capitol Hill.

Republican Rep. Adam Kinzinger of Illinois publicly called on Trump’s Cabinet to invoke the 25th Amendment and remove the president from office.

“The president caused this,” Kinzinger said in a video posted to Twitter. “The president is unwell.”

Sen. Lindsey Graham, R-S.C., did not join that effort but laid blame at the president's feet. Trump’s actions were the “problem” leading to the Capitol violence, he said.

Biden aide Andrew Bates said in a statement that the president-elect is focused on the transition “and will leave it to Vice President Pence, the Cabinet and the Congress to act as they see fit.”

The Republicans who led the effort to challenge the Electoral College tally for Biden exposed the extent of the divisions within the party, and the nation, after four years of Trump's presidency.

Those two GOP senators, Ted Cruz of Texas and Josh Hawley of Missouri, faced angry peers in the Senate.

Cruz defended his objection to the election results as “the right thing to do” as he tried unsuccessfully to have Congress launch an investigation.

In the House, Republican leaders Rep. Kevin McCarthy of California and Rep. Steve Scalise of Louisiana joined in the failed effort to overturn Biden's win by objecting to the Electoral College results.

Despite Trump’s repeated claims of voter fraud, election officials and his own former attorney general have said there were no problems on a scale that would change the outcome. All the states have certified their results as fair and accurate, by Republican and Democratic officials alike.

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Associated Press writers Mary Clare Jalonick, Zeke Miller, Alan Fram, Padmananda Rama and Michael Balsamo in Washington contributed to this report.