A mob of people stormed the US Capitol on Wednesday as weeks of President Donald Trump’s unfounded claims the 2020 election was stolen boiled over into a display of insurrection. The chaos, which included multiple reports that shots had been fired, came as Congress was assembled to affirm the election’s results.

Trump, who had spoken to a rally of supporters nearby, stirred up his fans, telling them “We will never give up, we will never concede.” The president also used Twitter to attack Vice President Mike Pence, who had earlier issued a statement saying that he couldn’t stop the congressional count of electoral votes, which is mandated by the Constitution.

“Mike Pence didn’t have the courage to do what should have been done to protect our Country and our Constitution,” Trump tweeted in a statement that falsely claimed fraudulent votes were certified by the states. “USA demands the truth!,” he continued. Twitter initially labeled the tweet as disputed, noting that users can’t reply to, retweet or like the tweet “due to a risk of violence.” The tweet is no longer available along with two other tweets Trump posted on Wednesday.

Trump, who lost the US presidential election to former Vice President Joe Biden, has been using Twitter and Facebook to push baseless claims about election fraud to his millions of followers. The companies have labeled several of Trump’s tweets and posts, but critics say those efforts do little to stop the spread of misinformation that could incite violence.

In a rare move, Twitter said it required removal of the three tweets from Trump’s account because they violated its rules against manipulating or interfering in elections and other civic processes. “This means that the account of @realDonaldTrump will be locked for 12 hours following the removal of these Tweets. If the Tweets are not removed, the account will remain locked,” Twitter said in a tweet. Twitter also added that Trump’s account will be permanently suspended if he violates the company’s rules again.

Social networks have typically been reluctant to remove Trump’s posts but politicians aren’t exempted from their rules against inciting violence. In the past, Twitter has added a notice to Trump’s tweets but allowed users to view his remarks because of public interest.

“Our public interest policy — which has guided our enforcement action in this area for years — ends where we believe the risk of harm is higher and/or more severe,” Twitter said in a tweet.

Facebook, which exempts politicians from fact-checking, also added labels to several of Trump’s posts directing users to its election information center before removing them. In a blog post, Facebook said it would also remove content that praised the storming of the US Capitol, calls to bring weapons to protests and calls for protests that violate DC’s 6 p.m. ET curfew called by the mayor.

By the time these companies acted though, Trump’s posts already garnered a lot of views. Earlier on Wednesday, Trump posted a video urging his supporters to “go home now.” “We have to have peace. We have to have law and order,” he said in the video in which he also repeated false claims about election fraud. The video racked up more than 13 million views on Twitter before it was taken down. Facebook and Google-owned YouTube pulled down the video.

Facebook’s VP of Integrity Guy Rosen said in a tweet the company removed Trump’s video because “we believe it contributes to rather than diminishes the risk of ongoing violence.” YouTube cited a policy of removing any new videos alleging fraud in the 2020 presidential election, as Trump’s video did. YouTube put the rule in place a month ago and it essentially categorized Biden’s victory and Trump’s loss as historical fact. YouTube said it would allow copies of the video to remain on the platform if it’s presented in the context of providing “sufficient educational, documentary, scientific, or artistic value.”

The White House didn’t respond to a request for comment.

On Wednesday, the social networks faced more calls to suspend Trump’s accounts and take stronger action against posts that incite violence. University of Virginia law professor Danielle Citron, journalist Kara Swisher, Obama Foundation CTO Leslie Miley, Anti-Defamation League CEO Jonathan Greenblatt and others posted tweets urging Twitter to boot Trump from the social media site.

“Time is now to suspend Trump’s account,” Citron tweeted. “He has deliberately incited violence, causing mayhem with his lies and threats.”

Twitter said in a statement it will take action against tweets that violate its rules. “Let us be clear: Threats of and calls to violence have no place on Twitter, and we will enforce our policies accordingly,” the company said. (Its tweets can be found here.)

Facebook, which also has rules against inciting violence, likewise faced criticism for allowing Trump and his supporters to push false claims of voter fraud on its site. Christopher Wylie, the whistleblower in Facebook’s Cambridge Analytica scandal, tweeted that the violence that broke out at the US Capitol was an “inevitable manifestation of the conspiracy, vitriol and hate fed to people daily on Facebook.”

Facebook said it’s reviewing and removing any content that violates its rules against inciting violence.

“The violent protests in the Capitol today are a disgrace. We prohibit incitement and calls for violence on our platform,” a Facebook spokesman said in a statement.

President-elect Joe Biden held a press conference just past 4 p.m. ET, calling the attack “chaos,” an “assault” on democracy and saying it “borders on sedition.” “I call on the mob to step back,” Biden said. “It’s not a protest, it’s an insurrection.”

Biden also called for Trump to appear on national TV to denounce their actions and tell them to stop. “President Trump, step up,” he said, adding the words of a president can “inspire” or they can “incite.”

Biden said he is not concerned about the safety and security of his inauguration later this month.

CNN reported that a woman was being treated for gunshot wounds on the Capitol grounds and showed video of rioters scampering through bashed-in windows. NBC later reported that the woman had died of her wounds.

Photos showed unprecedented scenes of the pro-Trump mob milling in the Capitol. In one photo, a member of the mob sat a desk that CNN identified as House Speaker Nancy Pelosi’s.

Biden addressed the nation, calling on Trump to do the same. “Our Democracy is under unprecedented assault,” Biden said.

Members of the House of Representatives and the Senate had gathered Wednesday to count the electoral votes transmitted by the states. Trump and some lawmakers sought to use the process, which is usually ceremonial, to challenge the results of the election. Trump had pressured Pence, who presides over the process, to support his unfounded claims the vote was stolen.

Hours before the vote count began, Trump tweeted that states wanted to correct their votes and repeated bogus claims of “irregularities and fraud.” He called on Pence to send the votes back to the states. “Do it Mike, this is a time for extreme courage!” he wrote in a tweet that was labeled as disputed.

Several reporters were tweeting from the scene, including Huffington Post’s Matt Fuller, Politico’s Olivia Beavers and Huffington Post’s Igor Bobic.

CNET’s Joan E. Solsman and Corinne Reichert contributed to this report.