Hundreds of supporters of former Brazilian President Jair Bolsonaro stormed three of the most emblematic official buildings in the country's capital over refusal to accept the results of the election.
The demonstrators partook in violent protests on Sunday at the Supreme Court, Congress and the presidential office, called the Planalto Palace, in Brasilia.
Right-wing supporters of the former Brazilian president were asking the new president, leftist Luiz Inácio Lula da Silva, to leave -- falsely claiming that he won in a "stolen election."
The unrest began when 100 buses full of Bolsonaro supporters arrived in the capital on Sunday for a planned protest.
Despite more than 4,000 protesters taking the streets of the capital, police presence was minimal.
Several hundred protestors broke police barriers and were able to enter the Chamber of Deputies and the Senate through the roof. Later, they were even able to break into the Planalto Palace.
All of these buildings were empty, as Lula was in Sao Paulo, and Congress and the Supreme Court are in recess until February.
Rioters were armed with sticks and committed vandalism, including destroying pieces of art such as Chinese porcelain vases in the president's office.
By 4 p.m. local time, cavalry police were sent for intervention and threw tear gas at protesters. Rubber bullets were also fired at the crowd.
So far, 400 people have been arrested, according to Brazilian Federal District Gov. Ibaneis Rocha.
Control of the buildings has since been reestablished, according to The Associated Press.
Bolsonaro, 67, is currently in Florida, where he traveled to just before Lula was sworn in as the 39th president of Brazil. Lula also served as the country's 35th president.
Lula, 77, said he will travel back to Brasilia Sunday and vowed to punish all invaders, including potential military police officers.
Lula also accused security forces of "incompetence, bad faith and malice, as they have been unable to stop rioters from accessing Congress."
He said there is "no precedent in the history of our country" regarding Sunday's events and described the violence as "acts of vandals and fascists."
The national guard is now in charge of restoring order in Brasilia.
In a series of tweets, Bolsonaro condemned the "depredations and invasions of public buildings," according to a translation of his tweet.
President Joe Biden condemned the violent assault on Sunday while traveling in El Paso, Texas, calling it "outrageous."
National Security Adviser Jake Sullivan tweeted, "The United States condemns any effort to undermine democracy in Brazil. President Biden is following the situation closely and our support for Brazil’s democratic institutions is unwavering. Brazil’s democracy will not be shaken by violence."
Secretary of State Antony Blinken said the U.S. condemns the attacks, writing: "Using violence to attack democratic institutions is always unacceptable. We join @lulaoficial in urging an immediate end to these actions."
ABC News' Julia Jacobo and Conor Finnegan contributed to this report.