Impeachment article has 200 cosponsors: US rep.

In a "Dear Colleague" letter Wednesday evening, House Speaker Nancy Pelosi called the breach of the U.S. Capitol "a shameful assault was made on our democracy" but said it wouldn't deter lawmakers from carrying out their duties.

"To that end, in consultation with Leader Hoyer and Whip Clyburn and after calls to the Pentagon, the Justice Department and the Vice President, we have decided we should proceed tonight at the Capitol once it is cleared for use," she wrote.

"We also knew that we would be a part of history in a positive way, today, despite ill-founded objections to the Electoral College vote. We now will be part of history, as such a shameful picture of our country was put out to the world, instigated at the highest level," Pelosi continued.

"Members and staff should remain on the Capitol complex until they are notified by the United States Capitol Police. I look forward to seeing you later this evening, during this time of great sadness," she said.

-ABC News' Mary Bruce

As the chaotic scene continued in the nation's capital with the world watching, Trump once again tweeted his repeated his false claim that the presidential election was being stolen from him and appeared to try to justify the storming of the U.S. Capitol that he encouraged earlier in the day.

"These are the things and events that happen when a sacred landslide election victory is so unceremoniously & viciously stripped away from great patriots who have been badly & unfairly treated for so long," he said.

"Remember this day forever!" he added.

Former President George W. Bush released a statement on what he called an "insurrection" at the U.S. Capitol, calling it "a sickening and heartbreaking sight."

"This is how election results are disputed in a banana republic – not our democratic republic. I am appalled by the reckless behavior of some political leaders since the election and by the lack of respect shown today for our institutions, our traditions, and our law enforcement," Bush said.

"The violent assault on the Capitol – and disruption of a Constitutionally-mandated meeting of Congress – was undertaken by people whose passions have been inflamed by falsehoods and false hopes. Insurrection could do grave damage to our Nation and reputation. In the United States of America, it is the fundamental responsibility of every patriotic citizen to support the rule of law. To those who are disappointed in the results of the election: Our country is more important than the politics of the moment. Let the officials elected by the people fulfill their duties and represent our voices in peace and safety," Bush continued.

He did not mention President Trump by name.

Ahead of the district-wide curfew, the entire D.C. National Guard, FBI Washington Field Office, U.S. Secret Service, Federal Protective Services and the Metropolitan Police Department are responding to the breach at the U.S. Capitol to assist Capitol Police, sources tell ABC News. Deputy U.S. Marshals are also being deployed to assist, according to a Justice Department official. Customs and Border Protection officers are being deployed as well.

Washington, D.C., Mayor Muriel Bowser issued a curfew beginning at 6 p.m. and ending Thursday at 6 a.m. earlier in the day -- but with minutes to go until that curfew, there are hundreds of pro-Trump supporters still on the streets, resisting calls from law enforcement and lawmakers to go home.

After nearly four hours of pro-Trump supporters breaching the building, officials have declared the U.S. Capitol is secure.

Here are images of what’s unfolding: