Thousands of armed Trump supporters are reportedly planning to target the US Capitol once more in a bid to disrupt president-elect Joe Biden's inauguration.
Members of Congress were briefed about the group's plans on Monday, with officials describing it as a "credible threat" to safety.
Congressman Conor Lamb told CNN the pro-Trump group have even advised those wishing to come on when they can and cannot fire their weapons.
"They were talking about 4000 armed 'patriots' to surround the Capitol and prevent any Democrat from going in," he said.
"They have published rules of engagement, meaning when you shoot and when you don't. So this is an organised group that has a plan.
"They are committed to doing what they're doing because I think in their minds, you know, they are patriots and they're talking about 1776 and so this is now a contest of wills."
That was the year the American colonies signed the Declaration of Independence. They went on to win their independence from Britain in the Revolutionary War.
This new threat comes just days after pro-Trump rioters smashed their way into the Capitol building, resulting in five deaths and forcing politicians inside to hide behind bulletproof chairs.
Lamb said there was no reasoning or negotiating with the group, calling for those involved to be prosecuted.
"They have to be stopped. And unfortunately, that includes the President, which is why he needs to be impeached and removed from office," he said.
"So to be clear, these are specific, credible threats that you've heard, that law enforcement believe are legitimate, and they're taking seriously and planning for?" host Alisyn Camerota asked.
"Yes," Lamb said.
Other Democratic politicians who were at the briefing told CNN that officials were taken through multiple different scenarios about what could happen if the group follows through with their plan.
"They are very strong when we are weak. That is when the mob psychology takes hold and they are emboldened, but when met with actual determined force, I think a lot of these fantasy world beliefs about what will happen when they come to Washington will melt away," one said.
The briefing comes as the FBI warned a string of armed protests are expected to take place across all 50 states later this week and could continue through to Biden's January 20 inauguration.
"Armed protests are being planned at all 50 state capitols from January 16 through at least January 20, and at the US Capitol from January 17 through January 20," read the bulletin, which was obtained by ABC News.
The group has reportedly also warned of a "huge uprising" if Congress attempts to remove Donald Trump using the 25th amendment.
On Tuesday, the United Nations called on political leaders, including Trump, not to incite violence ahead of Biden's inauguration.
The organisation has asked "political leaders not to encourage their followers to commit violence or to incite violence," UN spokesman Stephane Dujarric said.
He said the message was "universal", including for the US.
"We very much hope that there will be no violence, either before or during the inauguration on the 20th," Dujarric said.
"People who have disagreements (should) go through established constitutional processes."
Officials on both sides of the political line have accused Trump of inciting the violence that took place at the Capitol last week.
However, the President has since defended his actions, labelling the speech he gave before the riot "totally appropriate".
"People thought that what I said was totally appropriate," Trump said on Tuesday when asked whether he took any "personal responsibility" for his role in the attack.
"And if you look at what other people have said, politicians at a high level, about the riots during the summer. The horrible riots in Portland and Seattle and various other places, that was a real problem, what they said.
"But they've analysed my speech and my words and my final paragraph, and everybody thought it was totally appropriate."