After violent pro-Trump protesters stormed the US Capitol on Wednesday, a growing number of Republican leaders and Cabinet officials told CNN that they believe Donald Trump should be removed from office before January 20. Four of them called for the 25th Amendment to be invoked, and two others said the President should be impeached.

"He has to be impeached and removed," said one current Republican elected official.

A former senior official said the President's actions were egregious enough to remove him even with such a short time left in his tenure.

"I think this has been a huge shock to the system," said the former official. "How do you keep him in place for two weeks after this?"

By impeaching and removing Trump, even at this late stage of his term, the Senate could subsequently vote to disqualify Trump from ever holding federal office again. On the other hand, invoking the 25th Amendment would require Vice President Mike Pence and a majority of the Cabinet to vote to remove Trump from office due to his inability to "discharge the powers and duties of his office" -- an unprecedented step.

On Thursday morning, Rep. Adam Kinzinger of Illinois became the first Republican member of Congress to call for Trump's removal from office.

"It's time to invoke the 25th Amendment and end this nightmare," Kinzinger said in a video he published online.

Some Cabinet members are holding preliminary discussions about invoking the 25th Amendment, a well-placed GOP source told CNN Wednesday night.

The discussions are ongoing but it's unclear if there will be enough Cabinet members to result in Trump's removal. The conversations have reached Capitol Hill where some senators have been made aware of the discussions, the source said.

Within minutes of protestors breaching the Capitol on Wednesday afternoon, Republicans were revisiting the idea of removing Trump from office, a choice that nearly all of them passed on making a year ago during last year's impeachment trial.

The forceful denunciations of Trump are also unprecedented. Former President George W. Bush, who has kept a low profile, released a strongly-worded rebuke Wednesday evening calling the "insurrection" at the Capitol a "sickening and heartbreaking sight." While not mentioning Trump by name, Bush said he was "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."

Mitt Romney, the Utah senator who was the only Republican to vote to convict the President on an article of impeachment last year, went further, calling the President a "selfish man" who "deliberately misinformed his supporters" about the election. Romney also called the attack on the Capitol an "insurrection" and blamed Trump, saying he "stirred [supporters] to action this very morning."

Wyoming Republican Rep. Liz Cheney, a member of the House leadership, echoed Romney's anger and frustration at Trump. "There is no question that the President formed the mob. The President incited mob, the President addressed the mob," said Cheney on Fox News. "He lit the flame."

And Sen. Tom Cotton of Arkansas, an otherwise staunch ally of Trump's, was unsparing. "It's past time for the president to accept the results of the election, quit misleading the American people, and repudiate mob violence," Cotton said.

Other Republicans on Capitol Hill were furious as well with the President.

"The President needs to call it off," Rep. Mike Gallagher of Wisconsin told CNN's Jake Tapper. "Call it off! It's over. The election is over."

And Rep. Kinzinger dismissed Trump's Wednesday afternoon tweet asking rioters at the Capitol to "remain peaceful."

"That's cowardice," Kinzinger told Tapper. "He needs to stand up and say, I lost the election, let the count go ahead."

But as Trump seems unlikely to make those concessions, two longtime Republican activists and allies of the White House said the President must go.

"Pence should move against him on the 25th Amendment," said one.

"They need to invoke the 25th Amendment immediately," said the other.