A spokeswoman for the United States Capitol Police has confirmed to ABC News that Capitol Police Chief Steven Sund is resigning, effective Jan. 16.

The resignation comes after rioters seized the Capitol building on Wednesday and following House Speaker Nancy Pelosi calling for him to step down due to the botched response.

Sund does not mention the Capitol riot in his three-sentence resignation letter. "It has been a pleasure and true honor to serve the United States Capitol Police Board and the Congressional community alongside and the women and men of the United States Capitol Police," he wrote.

The Capitol Police Union had released a statement saying they were "frustrated and demoralized by the lack of leadership" and called for the chief and his deputy to resign.

"We have several protesters dead, multiple officers injured and the symbol of our Democracy, the U.S. Capitol, desecrated. This never should have happened," Capitol Police Union Chairman Gus Papathanasiou said in a statement.

"This lack of planning led to the greatest breach of the U.S. Capitol since the War of 1812," he added. This is a failure of leadership at the very top."

-ABC News' Mariam Khan, Benjamin Siegel and Luke Barr

More than 24 hours after a violent siege on the Capitol by supporters of the president, White House press secretary Kayleigh McEnany condemned the violence of the rioters who desecrated the hallowed halls of Congress "on behalf of the entire White House."

For the first time, she also recognized that there would be a new administration, although she did not mention Biden’s name, saying, “Those who are working in this building are working to ensure an orderly transition of power."

“Let me be clear. The violence we saw yesterday at our nation's Capitol was appalling, reprehensible and antithetical to the American way. We condemn it, the president and this administration, in the strongest possible terms. It is unacceptable,” McEnany said during remarks in the White House briefing room.

McEnany referred to those who stormed the Capitol as "violent rioters" and sought to draw a distinction between them and "the many thousands who came to peacefully have their voices heard in our nation's capital."

While she condemned the rioters, she did not acknowledge the role Trump had in inciting the mob and praising the insurrectionists. She also did not acknowledge her own role in repeatedly spreading disinformation about the election results.

McEnany read from prepared remarks, and the entirety of the event lasted just under two minutes.

She took no questions and exited as reporters shouted questions.

-ABC News' Ben Gittleson, Jordyn Phelps and Elizabeth Thomas

Trump has suggested to advisers that he wants to grant himself a pardon before leaving office, sources familiar with the discussions told ABC News.

The conversations with top aides have happened in recent weeks.

It's not clear if the issue has been discussed between the president and his advisers since the riots on Capitol Hill Wednesday.

However, following the riots Trump's White House Counsel, Pat Cipollone, advised the president that he could face legal jeopardy for encouraging his supporters to storm the Capitol building, according to sources familiar with their discussions.

If a self-pardon happens, it's unclear when it would be announced. Trump is already expected to issue several pardons over the next two weeks.

-ABC News' John Santucci, Katherine Faulders and Olivia Rubin

Five House Committees led by Democrats have sent a letter to FBI Director Christopher Wray seeking an "immediate briefing on the FBI's efforts to investigate the deadly attack on the US Capitol."

"We request an urgent briefing for the Chairs and Ranking Members of the undersigned Committees on how the FBI is working to investigate and hold responsible the domestic terrorists who incited and executed yesterday’s attack on the Capitol, as well as how the FBI has been tracking this domestic terrorist group, how it prepared for the events on January 6, 2021, and how it plans to disrupt any further violent plans," they wrote.

The letter was signed by Committee on Oversight and Reform Chair Carolyn Maloney, Committee on the Judiciary Chair Jerry Nadler, Committee on Homeland Security Chair Bennie Thompson, Permanent Select Committee on Intelligence Chair Adam Schiff, Committee on Armed Services Chair Adam Smith and Rep. Stephen Lynch.

“Given the incendiary environment caused and exacerbated by President Trump’s rhetoric, along with the upcoming inauguration of President-Elect Joe Biden, it is imperative that the FBI leverage all available assets and resources to ensure that the perpetrators of this domestic terrorist attack and those who incited and conspired with them are brought to justice, and that this domestic terrorist group is disrupted from further actions against our government,” the Chairs wrote in a press release.

According to the release, the letter detailed how Trump incited the attack on the Capitol by repeatedly making false claims about the election being "stolen."

-ABC News' Mariam Khan

Federal law enforcement officials have advised police agencies in state capitals to increase their security posture at statehouses around the country following the riot at the US Capitol, law enforcement sources told ABC News.

The concern, the sources said, is an emboldened right-wing that considered Wednesday a success and may next turn to locations in closer to home.

Like the U.S. Capitol, statehouses are often backdrops for demonstrations that law enforcement officials now fear could turn violent.

“The safety of the Massachusetts State House, its employees and its neighbors is of utmost importance. As we witness the events in Washington, DC and across the nation, we are aware of the need to ensure the safety of this building and those who work within it. We continually assess our security needs and will adjust as necessary,” said Massachusetts Gov. Charlie Baker, Senate President Karen Spilka and House Speaker Ronald Mariano in a joint statement.

Across the country in Washington state, Gov. Jay Inslee activated the National Guard to patrol the Capitol Campus when the state legislature convenes Monday.

“As legislators begin their work on behalf of the people of the state of Washington, we must do whatever we can to ensure that they can do that work without fear, intimidation or harassment. The actions we saw in both Washington, D.C. and Olympia earlier this week were completely unacceptable and will not be repeated in our state capital again,” Inslee said.

Security was also increased around the statehouse in Maryland, Gov. Larry Hogan said.

“Maryland State Police as well as Maryland Capitol Police, some of which you see around here, have increased security around the Maryland State House complex, since there’s been a number of incidents at state capitols and governor’s mansions around the country,” Hogan said.

-ABC News' Aaron Katersky and Josh Margolin