We're pausing our live coverage for now, but here's a recap on what happened on this busy Monday:

• Acting Homeland Security secretary Chad Wolf has announced he is stepping down
• Democrats have filed one impeachment article against Trump, charging that he incited his supporters to attack Congress
• Democrats have also called on Vice-President Mike Pence to eject Trump under the 25th Amendment to the US constitution
• While receiving his second vaccine dose, President-elect Biden pledged to hold "folks who engaged in sedition" accountable
• A Democratic lawmaker has tested positive for Covid-19 and believes she was infected while sheltering from rioters with other lawmakers last Wednesday
• Security is being stepped up ahead of Biden's inauguration on 20 January, with the National Guard authorising some 15,000 trooops to be deployed to DC

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In his letter to staff, circulated on social media, Chad Wolf said he had hoped to remain as acting secretary to homeland security until the end of the Trump administration.

"Unfortunately, this action is warranted by the recent events, including the ongoing and meritless court rulings regarding the validity of my authority as acting secretary," he said, "which serve to divert attention and resources away from the important work of the Department in this critical time of a transition of power".

Wolf's resignation comes after he last week called on Trump and all elected officials to "strongly condemn" the Capitol riot.

His exit throws the department into turmoil just as it is gearing up for inauguration of Joe Biden as president on 20 January, which has been designated a national security special event.

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The Secret Service had planned to lock down most of central Washington DC on the day before Joe Biden's inauguration on 20 January.

Now it will proceed with its security preparations six days earlier than originally scheduled, beginning this Wednesday.

On the same day he announced his resignation, acting Homeland Security Secretary Chad Wolf said the change of plans came "in light of events of the past week and the evolving security landscape leading up to the inauguration".

It comes on a day in which the National Guard said it would deploy up to 15,000 troops to the city to beef up security ahead of the formal presidential transition.

The Washington Monument has been closed to visitors and DC Mayor Muriel Bowser urged people to attend the ceremony virtually rather than in person.

Some news just in, acting Homeland Security Secretary Chad Wolf has announced he is stepping down, in a letter to his department.

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According to the DailyMail.com, Ivanka Trump is planning to attend Joe Biden’s inauguration on 20 January – upsetting her father in the process.

The news site quotes a White House insider as saying Ms Trump believes it will help “her own political aspirations” as she will come across as a “good sport and will gain future supporters”.

President Trump is said to be up in arms at his daughter’s decision. “'He said it's an insult that she would even want to engage with the crooks that are trying to bring him down,” the source says.

If Ms Trump does attend the inauguration, according to the insider, she will miss the launch of her father's campaign to reclaim the presidency in 2024 which is set for the same day.

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We previously reported that hotel chain Marriott International, health insurance company Blue Cross Blue Shield and financial powerhouse Citibank said they will withhold donations to Republican lawmakers who objected to certifying the election results last week.

Many more companies are now saying they will do the same.

They include accounting giant Deloitte, rental company Airbnb, telecom leader AT&T and credit card companies American Express and Mastercard.

Tech giants Facebook, Google and Microsoft joined banking giants JPMorgan Chase and Goldman Sachs in suspending all political giving for some amount of time, as did the Hilton Hotels chain, financial services firm Charles Schwab and manufacturing conglomerate 3M.

Greeting card manufacturer Hallmark - one of the largest employers in Kansas City, Missouri - is demanding refunds from two Republican senators who objected to the election results.

Other companies like Bank of America and the Ford Motor Company said they would take voting records into consideration before any future campaign contributions.

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Let’s look in more detail at the charges against President Trump contained in the resolution brought by the Democrats seeking to invoke the 25th Amendment, external.

It says “the insurrectionary mob” threatened the lives of the vice-president, the speaker of the house and others when Mr Trump tweeted disparaging remarks about Mike Pence "after the Capitol had been overrun and the Vice President was in hiding".

The “insurrectionary protests were widely advertised and broadly encouraged by President Donald J Trump” through his social media following and by promising activists the day “would be wild”.

Mr Trump and his family held a “celebratory kick-off rally to encourage and charge up the rioters and insurrectionists” before they moved on the Capitol.

The charge sheet goes on to say Mr Trump “ignored or rejected repeated real-time entreaties… to appeal to his followers to exit the Capitol”.

One particular sentiment that describes the violence comes from Republican senator - and frequent Trump defender - Lindsey Graham.

‘‘The mob could have blown the building up. They could have killed us all."

The House will return tomorrow to debate and vote on the resolution but it is unlikely to advance any further.

What is the 25th Amendment?

The family of Capitol police officer Brian Sicknick, who died after being injured while defending Congress against rioters, have just released a moving statement.

"There really aren't enough kind words in any language to describe how sweet Brian was," say his family. "He was truly a lovely, humble soul. We are missing him terribly."

"He was sweet natured through and through. Everyone who met him adored him," the statement continues.

"He loved his job with the US Capitol Police, and was very passionate about it. He also had an incredible work ethic."

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Congresswoman Linda Sanchez says she is "working on a bill that would mean that nothing - not even a bench, no airport, no highway, no school - nothing - ever bear the name" of President Donald Trump.

Sanchez - a Democrat from California - was among the lawmakers under siege at the US Capitol last Wednesday.

In her own retelling, she and her staff barricaded themselves inside their office rooms and grabbed baseball bats - from her time as a player on the Congressional Women's Softball team - to protect themselves from the mob.

“I don't believe that a seditious occupant of the White House should ever have anything named after him," said Sanchez. "I don't think that he deserves any of the benefits that are conferred on prior presidents.”

Her Democratic colleague Joaquin Castro is introducing similar legislation to prevent the Trump name going up on any federal buildings or property.

Explaining his decision, Castro said: "Let us learn from our past. Donald Trump should never become a future generation’s confederate symbol."

A US Capitol police officer is being called a hero for singlehandedly steering a mob away from the Senate chambers during last week's deadly riots.

Footage of the officer, identified as Eugene Goodman, shows him just steps ahead of rioters as they chase him up a flight of stairs.

Mr Goodman is then seen glancing toward the Senate entrance before luring the men in the opposite direction.

Footage shows a mob chasing Mr Goodman up a flight of stairs - just a few feet away from the entrance to the Senate floor. As he is pursued, Mr Goodman shouts "second floor!" into his radio, seemingly alerting other officers of the group approaching the chamber.

After Mr Goodman glances toward the Senate chamber entrance, he shoves one of the assailants - a move seemingly designed to draw attention onto himself - luring the mob away from the chambers and those hiding inside.

The officer has been celebrated by several members of Congress, with some calling for Mr Goodman to be awarded the Congressional medal of honour for his service.

Read more:

Capitol police officer Eugene Goodman heralded as 'a hero'

A majority of voters say Trump should resign, according to a new opinion poll from Quinnipiac University, external, with 56% respondents saying that they hold Trump responsible for the riot on Capitol Hill.

The poll also found that Trump's approval rating has dropped 11% since last month.

He is now at an all-time low of 33% favourable and 60% unfavourable, according to the survey.

The survey of 1,239 registered voters was conducted from 7 to 10 January.

A separate poll from Politico and Morning Consult, external also found last week that Trump's ratings appear to have fallen to the lowest point of his entire presidency.

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Members of the US National Guard have been deployed to the US Capitol building.

Some were seen taking pictures of the monuments and taking a break on the steps that were occupied by rioters last week.

Another 10,000 will arrive on Saturday as the FBI warns of the risk of more violence from armed extremists holding pro-Trump events in 50 state capitols between now and inauguration next week.

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After receiving his second and final dose of the Covid-19 vaccine, Biden tells reporters that he has spoken to senators about holding an impeachment trial while also confirming his Cabinet appointments.

He says he discussed the possibility that the Senate, which Democrats will soon control, may do a half-day of each.

"I think it is critically important that there be a real, serious focus on holding those folks who engaged in sedition and threatened peoples lives, defaced public property, caused great damage - that they they be held accountable," he says while putting on his coat.

President Trump is accused of "incitement of insurrection" related to the invasion of the US Capitol last Wednesday.

There have been fears among some Democrats that a Senate trial could hinder Biden as he tries to begin his first term at a rapid pace, with tackling the pandemic his top priority.

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Washington DC Mayor Muriel Bowser is urging people to avoid coming to the city for Joe Biden's presidential inauguration on 20 January.

She says people should participate virtually instead.

At a news conference on Monday, Bowser said her goal was “to protect the District of Columbia from a repeat of the violent insurrection experienced at the Capitol and its grounds”.

In recent days, she has called for federal agencies to beef up security preparations for the ceremony. She also said President Trump must declare a pre-emergency declaration so the city can coordinate resources with the government.

Activists have also taken to social media to urge rental property owners not to list their homes in the days leading up to the event.

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The Pentagon will release up to 15,000 National Guard troops to Washington DC to support Joe Biden's inauguration.

General Daniel Hokanson - chief of the National Guard Bureau - said the Department of Defense has authorised the move and about 10,000 troops will be in the city by Saturday.

The inauguration is next Wednesday but more pro-Trump protests are planned in the days leading up to it.

Questions remain over how long it took for the National Guard to be deployed last week when Trump supporters overwhelmed local police to storm the Capitol.

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President Trump is to award the Presidential Medal of Freedom – the nation’s highest civilian honour - to Ohio Republican representative Jim Jordan, one of his most loyal allies in Congress.

The White House, in its statement announcing the award, external, listed Mr Jordan’s achievements, which included working “to unmask the Russia hoax and take on Deep State corruption” and “unearth malfeasance at the highest levels of the United States Government”, and lead the “effort to confront the impeachment witch hunt”.

“He is an inspiration to freedom-loving Americans everywhere,” the White House added.

The president, who has not spoken in public since last Wednesday, will give the medal to Mr Jordan in a closed-door ceremony.

Jordan was one of dozens of Republican lawmakers who voted to block Biden’s victory. He cast his vote even after rioters disputing the election had stormed the building.

President-elect Joe Biden, who will be sworn in next Wednesday, has just received his second dose of the Pfizer/BioNTech coronavirus vaccine.

The second jab was administered by the chief nurse at a hospital near his home in Delaware, according to his transition team.

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In one of its final acts under the Trump administration, the State Department will add Cuba back to its state sponsors of terrorism list.

The list singles out "countries determined by the secretary of state to have repeatedly provided support for acts of international terrorism", according to the State Department.

Cuba was put on the list in 1982, but the Obama administration took it off in 2015 as it sought to ease economic and travel restrictions on the island nation.

However, Trump administration officials labelled the Caribbean island state as part of a "troika of tyranny" in Latin America. It says the country has not cooperated in US counterterrorism efforts.

Placing Cuba back on the list is a lengthy process and it will hinder President-elect Joe Biden's goal of normalising relations with the country.

The state sponsors of terrorism list currently includes Syria, Iran and North Korea (added back to the list in 2017 under President Trump). In December, the administration took Sudan off the list.

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US Congresswoman Bonnie Watson Coleman says she has tested positive for Covid-19 – and believes she caught it while sheltering from rioters in the Capitol building last Wednesday.

“I received a positive test result for Covid-19, and am home resting at this time. While I am experiencing mild, cold-like symptoms, I remain in good spirits and will continue to work on behalf of my constituents,” she said, external.

The Capitol’s physician Dr Brian Moynihan warned on Sunday that “many members of the House community were in protective isolation in the large room – some for several hours," and said “individuals may have been exposed to another occupant with coronavirus infection”.

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An internal FBI bulletin is warning state and local law enforcement that they should prepare for violence by right-wing extremists on Sunday, according to US media who've seen the document.

The FBI memo - reportedly issued a week before last week's attack on the US Capitol - identifies credible threats to the US Capitol and all 50 state capitols, from 16 January to 20 January.

A violent far-right group known as the Boogaloo is behind these organising efforts, according to the document.

It states the Boogaloo movement believes "an impending insurgency against the government is forthcoming, and some believe they should accelerate the timeline with armed, anti-government actions leading to a civil war".

Members of the movement are calling for the “storming” of state, local and federal government courthouses and administrative buildings ahead of Joe Biden's inauguration next Wednesday - and on the day itself.

Who are the Boogaloo Bois?

The FBI is currently reviewing over 40,000 digital media tips received from the public in recent days, after it appealed for help identifying rioters who joined the Capitol unrest.