Former President Donald Trump is expected to travel to New York on Monday, sources familiar with the matter told ABC News.

He is expected to appear in court on Tuesday at the earliest, the sources said, on what is expected to be around two dozen counts - including felonies.

The exact charges are unknown since the indictment will not be unsealed until Trump appears in court.

-ABC News’ Aaron Katersky, Katherine Faulders, John Santucci

As legal experts speculate on what charges lay inside the sealed indictment ahead of former President Donald Trump's expected surrender on Tuesday afternoon, many predict that prosecutors could try out a new legal theory to justify bringing the charges.

"This could be a novel legal theory," said Kate Shaw, a law professor at Cardozo and ABC News contributor, speculating on what charges the public could see against Trump while stressing it's unknown until the indictment is unsealed.

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-ABC News' Libby Cathey

Former President Donald Trump has been charged with around two dozen counts, including felonies, sources familiar with the sealed indictment told ABC News.

The exact charges remain unknown since the indictment will not be unsealed until Trump appears in court on Tuesday.

The Manhattan district attorney’s office declined to comment.

The Senate sergeant at arms is warning of potential demonstration activity related to the indictment of former President Donald Trump.

"While law enforcement is not tracking any specific, credible threats against the Capitol or state offices, there is potential for demonstration activity," an email obtained by ABC News said.

Capitol Police "is working with law enforcement partners, so you may observe a greater law enforcement presence on Capitol Hill," the email said, adding that there could be "nationwide impacts to Senate state offices."

The Capitol Police declined to comment and the sergeant at arms didn't immediately respond to ABC News' request for comment.

-ABC News' Luke Barr

Some of Trump's confirmed or prospective rivals for the 2024 Republican presidential nomination were among those who spoke out Thursday night in the wake of the news of the former president's indictment.

In an interview with CNN on Thursday night, former Vice President Mike Pence called it an "outrage," arguing that the case against Trump is "tenuous" and will "only further serve to divide our country."

Florida Gov. Ron DeSantis, whom sources have told ABC News is expected to launch a presidential campaign in the coming months, tweeted that the indictment was "un-American" and "a weaponization of the legal system," adding that Florida would "not assist in an extradition request."

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-ABC News' Alexandra Hutzler and Mariam Khan