D.C. Mayor Muriel Bowser is among regional leaders who responded to the shocking storming of the U.S. Capitol on Wednesday by supporters of President Donald Trump. The breach halted the counting of Electoral College votes for President-elect Joe Biden.
Rioters used chemical irritants on police in order to gain access to Capitol grounds, and multiple D.C. police officers have been injured, D.C.'s Acting Chief of Police Robert Contee said at a news conference.
"The behavior that we are witnessing is shameful, unpatriotic, and above all, it is unlawful," Bowser said at a press conference late Wednesday afternoon. "Anyone who has engaged in these activities, continues in these activities, will be held accountable. There will be law and order, and this behavior will not be tolerated."
Law enforcement appeared to use flash bang devices with chemical irritants to try to scatter protesters. People could be seen walking down the Capitol steps in clouds of smoke. About 6 p.m., officials declared the U.S. Capitol complex secure after heavily armed police moved to end a violent, nearly four-hour occupation.
The D.C. National Guard, as well as the Maryland and Virginia national guards, Virginia state troopers and Maryland state troopers, were mobilized to respond to the Capitol.
"All Americans should be outraged by this attack on our nation's Capitol," Maryland Gov. Larry Hogan wrote on Twitter. "This is a heinous and violent assault on the heart of our democracy. I will not stand for this, and neither should any American."
Both Hogan and Virginia Gov. Ralph Northam were mobilizing forces within their states to respond to the situation at the Capitol.
Hogan said he has directed Maryland State Police to send in troopers and told the Maryland National Guard to call up a rapid response force "to support law enforcement and restore order."
Maryland's and Virginia's responses will assist Washington, D.C.'s Metropolitan Police Department and the U.S. Capitol Police.
Northam said he was working closely with Bowser, House Speaker Nancy Pelosi and Sen. Chuck Schumer to respond to the situation.
"Per the Mayor's request, I am sending members of the Virginia National Guard along with 200 Virginia State Troopers," Northam posted on Twitter.
Northam denounced the actions of the rioters at the Capitol, releasing a statement Wednesday night saying in part, "This did not come about overnight. When elected leaders purposefully reject facts and fan the flames of conspiracy theories, all in pursuit of power, they are taking dangerous steps. And now we are seeing where those steps can lead. God forbid we experience anything worse."
Northam also declared a curfew for Arlington County and the City of Alexandria "with limited exceptions," he wrote on Twitter. The curfew began at 6 p.m. Wednesday and will continue until 6 a.m. Thursday.
"I am also issuing a State of Emergency in Virginia, so we can continue to respond," Northam wrote.
In a statement, U.S. Rep. Jennifer Wexton, D-Va., denounced Trump and called for his removal from office.
“The President has been encouraging these domestic terrorists since before the election," she said. “He could have stopped them at any moment, but instead he whipped them into a frenzy and sicced them on the Capitol. The Cabinet must remove him today or the House must impeach.”
Stay with NBC Washington on this developing story.