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

Former President Donald Trump's daughter, Ivanka Trump, reacted to the indictment on Instagram Friday, writing, "I love my father, and I love my country. Today, I am pained for both."

She added, "I appreciate the voices across the political spectrum expressing support and concern."

Sources familiar with the matter told ABC News the Manhattan district attorney’s office is also investigating a $150,000 payment to Playboy model Karen McDougal, who, like Stormy Daniels, claimed to have had an affair with Donald Trump.

The former president has denied having an affair with either woman and has called the investigation a witch hunt.

McDougal was paid for the rights to her story in August 2016 by American Media, publisher of the National Enquirer, which did not publish it, a practice known as catch and kill.

Michael Cohen, Trump’s former lawyer and fixer, has said he recorded Trump discussing reimbursement to American Media for the payment to McDougal, but the payment was never made.

Trump has not responded to ABC News' request for comment but in a 2018 interview with Fox News, he claimed he wasn't aware of any payment made to AMI to facilitate the alleged hush agreement.

A white powder was discovered in the mailroom at 80 Centre Street, where the Manhattan District Attorney has offices and where a grand jury has been meeting to hear evidence in former President Donald Trump's case, according to a court official. The powder was determined to be non-hazardous, officials said.

The powder came in an envelope addressed to "Alvin," an apparent reference to Manhattan District Attorney Alvin Bragg, according police sources.

Inside the envelope was a letter containing the typewritten message, “Alvin: I am going to kill you," with 13 exclamation points, according to sources.

This envelope followed a series of unfounded threats that targeted municipal offices in New York this week.

"For three days we got four emails," Susan Stetzer, district manager at Manhattan Community Board 3, told ABC News on Friday.

At least one of the messages prompted the court to pause a hearing in the New York Attorney General’s civil lawsuit against Trump.

None of the email messages mentioned Trump by name. One included what Stetzer described as a "horrible homophobic rant."

According to Stetzer, the messages came from @mail.ru domains and some contained Cyrillic characters. The FBI is aware but does not immediately assess that the emails came from Russia, according to a law enforcement official.

"We did not get one today so I’m hoping it stops," Stetzer said.

New York City courthouses will see increased security, the Office of Court Administration said Friday.