Long before Sunday's shocking attack on Brazil's Congress and other government buildings, warning signs on social media pointed to possible violence by backers of former President Jair Bolsonaro — one of several important parallels with the Jan. 6 attack on the U.S. Capitol two years ago.

The similarities run deep: In addition to the aim of subverting an election, some of the same U.S. voices that amplified then-President Donald Trump's false claims of a stolen election before the Capitol assault have also sought to sow doubt over Bolsonaro's loss to Brazil's new president, Luiz Inácio Lula da Silva.

In the space of 24 hours over Sunday and Monday, former Trump political adviser Steve Bannon said no fewer than 10 times on the right-wing social media platform Gettr that Lula "stole the election." When he shared images from Brasilia on Sunday showing the houses of Brazil's democracy under attack, Bannon labeled the insurrectionists "freedom fighters."

Since before the October election, Bannon has been hosting guests on his popular podcast warning about fraud in Brazil and promoting accusations that voting had been compromised.

Other U.S. election deniers also weighed in. Ali Alexander, a leading organizer of the Stop the Steal movement contesting the 2020 presidential election, called Brazil's Supreme Court "illegitimate" and urged Brazilians to "do whatever is necessary."

"These movements mutually feed off of each other. Many of these right-wing individuals found a kindred spirit in what Donald Trump was trying to do to the United States during his presidency," said Sergio Guzmán, director of Colombia Risk Analysis, who monitors the political climate in Latin America.

Brasília attack was coordinated on social media platforms

Bolsonaro's allies have long used WhatsApp and other digital tools to spread viral lies and hoaxes that might boost his support.

"Since 2016, the former president and his supporters have been using social media and messaging apps to distort political, economic and social narratives, creating a parallel reality where all these people seem to be trapped," wrote Natália Leal, the CEO of Brazilian fact-checking site Agência Lupa, on Monday.

After Lula was sworn in, the goal shifted to planning an assault on Congress, the judiciary and the presidential palace, according to Brazilian news reports and researchers who study online platforms.

In the days before the attack, many messages used a code term to refer to the plan: "Festa da Selma," or "Selma's party," reported the newspaper O Globo, citing information from the data analysis company Palver. The phrase is a play on the Portuguese word selva, a term associated with Brazil's military, in what researchers say appears to be a coded attempt to avoid detection by social media companies and authorities.

Use of the term in WhatsApp groups dedicated to Brazilian politics began on Dec. 27 and rose in the following week, according to Agência Lupa. Similar messages appeared on Twitter, TikTok and Facebook, Lupa reported.

Some messages included tactical and strategic advice, O Globo reported, including a proviso that no protesters should attempt to breach one of the branches of government before the crowd's size had reached a critical mass that would let it attempt to seize control of all three government facilities at once.

On Telegram, posts appearing as early as Jan. 3 promised Bolsonaristas an expenses-paid trip to Brasília to bolster the protesters' numbers, the newspaper Estadão reported.

As the chaos unfolded on Sunday, YouTube users livestreamed from Brasília, attracting more protesters as well as financial contributions to the livestreamers, according to Lupa.

Facebook says the Brasília assault is a "violating event"

Responding to NPR's request for comment on how it has handled speech and postings around Bolsonaro supporters' attempts to disrupt the government, a spokesperson for Facebook parent Meta says it has been "removing content calling for people to take up arms or forcibly invade Congress, the Presidential palace and other federal buildings."

Even before the election, spokesperson Andy Stone said, Meta classified Brazil as a "temporary high-risk location."

Sunday's storm of government buildings was designated "as a violating event," Stone added, meaning Meta's monitors are removing any content seen as supporting or praising the brief takeover.

YouTube and Twitter said they are removing content that violates their rules, including posts and videos inciting violence.

Meta and Twitter said they are in touch with Brazilian authorities about their investigations.

TikTok and Telegram didn't respond to requests for comment.

Brazil's government has tried to crack down on false election claims and can force social networks to take down posts and even ban election deniers.

On Sunday night, Brazilian Supreme Court Justice Alexandre de Moraes issued an order calling on Facebook, Instagram, TikTok and Twitter to block a total of 17 accounts that the court says are linked to the attacks.

But posts circulate quickly across platforms — with Telegram messages reshared to WhatsApp and Facebook and with TikTok videos popping up on Twitter — creating a cycle of amplification that makes it difficult for any one company to address.

Brazil has been fertile ground for America's far right

Before Sunday's violence, red flags were raised in Brazil in September 2021, when tens of thousands of supporters answered Bolsonaro's call to march on the Supreme Court in Brasília. Protesters attempted to breach barricades, but they were thwarted by a large police and military presence.

That crisis played out as Trump allies and other U.S. conservatives visited Brazil to attend a Conservative Political Action Conference being held there. They included Gettr CEO Jason Miller, a former Trump adviser whose company sponsored the Brazilian version of the American Conservative Union-backed conference.

Just two months after launching Gettr, Miller said, Brazil was "already the second-largest country for us," after the U.S., according to an interview on Bannon's War Room podcast. He noted that some Bolsonaro supporters had been "deplatformed" by other tech companies.

Bolsonaro followed Trump's playbook after losing the election

Lula was sworn in on Jan. 1, a transfer of power that took place without Bolsonaro, who days earlier left Brazil for Florida. It was one of many ways in which Bolsonaro has mirrored Trump, who also refused to attend the swearing-in ceremony of his successor.

At the time, Bolsonaro's U.S. trip was widely seen as a strategy to avoid criminal charges related to his actions in office, as he faces several potential investigations. But after Sunday's attacks, experts say Bolsonaro's presence in Florida could also preserve his hopes for a return to power.

"He's left the country so to not be held responsible during the attacks," Oliver Stuenkel of the Getulio Vargas Foundation in Brazil told NPR's Morning Edition, "because the electoral justice system has made clear that if he explicitly incites his followers, he may lose his political rights."

In that, Stuenkel said, Bolsonaro has been more careful than Trump. But because of the many similarities between the two politicians, Stuenkel said, it was no surprise that a "January 6 scenario" unfolded in Brazil.

"When January 6 happened, Bolsonaro's son actually publicly came out rooting for the invaders and even said that if they had organized better, they could have achieved most of their aims," Stuenkel said.