Before introducing his Justice Department picks from Wilmington, Delaware, on Thursday, Biden offered comments on Wednesday's chaos at the Capitol which he deemed "one of the darkest days in the history of our nation" and "an unprecedented assault on our democracy."

"All of us here grieve the loss of life, grieve the desecration of the people's house. But what we witnessed yesterday was not dissent. It was not disorder. It was not protests. It was chaos," Biden said. "They weren't protesters. Don't dare call them protesters. They were a riotous mob, insurrectionists, domestic terrorists."

Biden placed blame on Trump who, he said, for the past four years has "made his contempt for our democracy, our Constitution, the rule of law clear in everything he has done."

"He unleashed an all-out assault on our institutions of our democracy from the outset. And yesterday was but the culmination of that unrelenting attack," Biden said.

Biden also predicted the response would have been very different had the majority of rioters been Black.

"No one can tell me that if it had been a group of Black Lives Matter protesting yesterday, there wouldn't have been -- they would have been treated very, very differently than the mob of thugs that stormed the Capitol. We all know that's true, and it is unacceptable, totally unacceptable," he said.

House Speaker Nancy Pelosi has called on Vice President Mike Pence to invoke the 25th Amendment to remove Trump from office for his "seditious acts" following Wednesday's rioting at the Capitol, she said at a press conference Thursday.

The California Democrat is threatening impeachment proceedings if Pence does not.

-ABC News' Mariam Khan

Senate Majority Leader Mitch McConnell put out a statement Thursday, saying the riots within the Capitol Building Wednesday represent "a massive failure" of "institutions, protocols, and planning that are supposed to protect the first branch of our federal government."

"A painstaking investigation and thorough review must now take place and significant changes must follow," McConnell added. "Initial bipartisan discussions have already begun among committees of oversight and Congressional Leadership."

-ABC News' Allison Pecorin

Transportation Secretary Elaine Chao is resigning from her position in the wake of rioting at the U.S. Capitol.

She cites the storming of the Capitol by "supporters of the President" as an "entirely avoidable event" in a letter she is sending out to her colleagues announcing her resignation.

"Yesterday, our country experienced a traumatic and entirely avoidable event as supporters of the President stormed the Capitol building following a rally he addressed. As I'm sure is the case with many of you, it has deeply troubled me in a way that I simply cannot set aside," Chao said.

Chao is married to Senate Majority Leader Mitch McConnell.

At District of Columbia Mayor Muriel Bowser's request, Army Secretary Ryan McCarthy has activated about 340 unarmed D.C. National Guardsmen to assist local law enforcement with the demonstrations taking place on Wednesday pegged to the Electoral College certification.

"We think it's helpful to have our D.C. Guardsmen, who are our Guard, that I have requested from the Secretary of the Army to assist MPD [Metropolitan Police Department] with traffic management," Bowser said Monday. "It absolutely frees up more officers."

The D.C. Guard is unique in that any call-ups have to be made by the Army secretary and not the jurisdiction’s top elected official -- as is the case with state governors. Additionally, more focus has been given to the call-ups since the controversial presence of D.C. Guardsmen and the use of D.C. Guard helicopters during the Black Lives Matter demonstrations last summer.

"They will be deployed to assist us with crowd management, as well as traffic control in our nation's capital that will allow for the police officers to focus on anyone who's intent on instigating agitating or participating in violence in our city," said D.C. Police Chief Robert Contee. He also labeled any possibility of violence surrounding the protests as "unacceptable" and repeated that carrying firearms is not allowed under D.C. law.

A senior defense official said Bowser put in the request for Guardsmen on Dec. 31 and that it was approved Monday morning. Beginning Tuesday through Thursday, the 340 personnel will help man 30 traffic control checkpoints around the northern side of the downtown area close to the National Mall.

"No one's going to be armed or body armor or anything like that," said the official. "What they need is traffic control."

-ABC News' Luis Martinez and Quinn Owen