Manhattan District Attorney Alvin Bragg's office said in a statement that it has contacted former President Donald Trump's attorney "to coordinate his surrender" for arraignment on a state Supreme Court indictment, noting that it remains under seal.

"Guidance will be provided when the arraignment date is selected," the office said.

In the wake of the indictment, all officers with the New York Police Department have been ordered to show up in uniform Friday morning for deployments around New York City, police sources told ABC News.

There are no credible threats, according to the mayor's office.

The indictment of Donald Trump marks an unprecedented development in the country's history -- the first time a former president has ever faced criminal charges.

Historians say that not since Richard Nixon had there been the real prospect of a commander-in-chief being formally accused of a crime, though Nixon avoided that fate after being pardoned by successor Gerald Ford.

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-ABC News' Tal Axelrod

Republican National Committee Chairwoman Ronna McDaniel called the indictment "a blatant abuse of power from a DA focused on political vengeance."

"When our justice system is weaponized as a political tool, it endangers all of us," she tweeted.

House Speaker Kevin McCarthy said in a tweet that the House GOP will use its power to hold Manhattan District Attorney Alvin Bragg "and his unprecedented abuse of power to account."

"The American people will not tolerate this injustice," McCarthy said, adding that Bragg has "weaponized our sacred system of justice against President Donald Trump."

House Republicans have requested documents and testimony from the Manhattan District Attorney's Office in its investigation of Trump, but Bragg has said he won't comply.

-ABC News' Lauren Peller