WASHINGTON, D.C. — Protesters challenging the election of Joe Biden stormed the U.S. Capitol and pounded on the door of the House chamber Wednesday, interrupting lawmakers who had been trying to count the Electoral College vote, an extraordinary moment spurred by President Donald Trump’s protest of the election results.

Tear gas was deployed in the Capitol building. Protesters broke the glass door of the chamber of the House floor, prompting plainclothes Capitol Police officers inside the House chamber to draw their guns. Members of Congress and Capitol Police officers blocked the door to the House chamber with a large bookcase. A single gunshot was heard in the chamber.

The House and Senate went into sudden recess and Vice President Mike Pence was escorted out of the presiding chair of the Senate chamber as the Capitol went into a complete lockdown. Photos posted online showed protesters on the second floor of the Senate side of the Capitol, indicating they had breached several layers of security and were within feet of senators. C-SPAN video showed dozens of protesters, some holding Trump flags, walking through Statuary Hall, which is typically highly secured.

Rep. Norma Torres, D-Calif., one of the lawmakers who was in the House chamber, described the experience as “horrible.”

“Trump has called homegrown terrorists to come to the Capitol and invalidate people’s votes,” she said. “U.S. citizens voted for Joe Biden and Kamala Harris.”

Lawmakers, aides and reporters were ordered to shelter in place. Although protests are somewhat common at the Capitol, the breach was unprecedented in recent history.

“I just had to evacuate my office because of a pipe bomb reported outside. Supporters of the President are trying to force their way into the Capitol and I can hear what sounds like multiple gunshots,” Rep. Elaine Luria, D-Va., wrote on Twitter.

The protests and violence occurred as a minority of Republicans objected to Congress’ counting of the electoral college votes, a formality required by the Constitution. It is typically a perfunctory process.

Republicans in both the House and Senate planned to object to the certified electoral vote tallies in at least three states, using the process to express their loyalty to Trump, who is urging them to protest in support of his baseless claims of voter fraud in the 2020 election.

There is no chance that the effort to block Biden from the presidency will succeed. With a Democratic majority in the House and upward of two dozen Republicans prepared to vote down the effort in the Senate, all objections will fail.

The challenge was well in the works even before Tuesday’s Senate runoff election in Georgia, where Democrats won one seat and are ahead in the other race. If they win both races, Democrats will seize the Senate majority from Republicans.

Wednesday’s Electoral College challenge will lay bare the internal divisions within the GOP. Though some high-profile conservatives are lining up to support Trump, others in the GOP are bitterly opposed to the last-ditch effort, highlighting the deep fractures opened in the Republican Party by the Trump presidency.

The objections will force Vice President Mike Pence into perhaps the most uncomfortable position of all. While seen as one of Trump’s most loyal allies, the vice president is responsible for overseeing the process on Capitol Hill as president of the Senate. Trump falsely said Tuesday that Pence can singlehandedly “reject” the victory, but Pence and others have noted he has no power to change the outcome.

On Twitter, Trump called his followers to come to Washington for the proceedings. Many of them did, filling a plaza near the White House on Tuesday evening.

The process got underway at 1 p.m. Eastern as a joint session of Congress met to go through each state in alphabetical order. Republicans planned to object to the results in at least three states: Arizona, Georgia and Pennsylvania.

For each objection, the House and Senate was to separate into their respective chambers for up to two hours of debate on the objection, followed by a vote on whether to uphold it.

Democrats universally reject the GOP claims and have expressed concern that the objections will have long-term consequences.

“These actions have eroded the American people’s faith in the integrity of our elections and the institutions that stand at the core of our democracy,” said Sen. Chris Coons, D-Del.

Republicans who object to the vote say they’re following through on the objections and concerns of their constituents. Rep. Doug LaMalfa, R-Calif., said he would have preferred courts to review claims of fraud.

“Because the courts at all levels have sidestepped their duty to the republic, there is no other alternative than to use the power of Congress to investigate and hopefully get to the truth,” LaMalfa said.

Numerous courts nationwide received and reviewed challenges pertaining to the vote — including the Supreme Court. All of them dismissed the claims.

Republicans who planned to object to the process include conservatives such as Sens. Josh Hawley of Missouri and Ted Cruz of Texas, and Rep. Mike Garcia of California, who was recently elected to his first full term.

Other Republicans say they have seen no evidence of fraud and cannot object, pointing to the states’ right to certify their own elections without interference from the federal government or other states.

Sen. Kevin Cramer, R-N.D., one of Trump’s most loyal allies in the Senate, said he has concerns about the widespread use of mail-in voting, but would prefer an independent commission to review the voting process — not to overturn the election.

“While I share the concerns of those who plan to object, the founding fathers did not design a system where the federal legislative branch could reject a state’s certified choice for president in favor of their own,” Cramer said.

Objections can only advance if they are supported by at least one House member and one senator. The most recent such objection was raised in 2005 upon the reelection of President George W. Bush, with the support of then-Sen. Barbara Boxer. The objection was heard, briefly debated and voted down.