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.

Donald Trump's former personal attorney and fixer Michael Cohen said the ex-president is likely "seething" over the indictment because he's "never been held accountable."

"The fact that he is being held accountable, something that he has no desire to ever be. He's never been held accountable," Cohen told ABC News' George Stephanopoulos in an interview Friday on "Good Morning America."

"This is a man who held up the Bible and said he's never apologized to God because he's never done anything wrong," he added. "He doesn't understand accountability. And right now, [Manhattan District Attorney] Alvin Bragg has finally put that into his lap."

Cohen, who is now estranged from Trump and is a key prosecution witness, said he decided years ago that his "loyalty can no longer be to a man who doesn't deserve it."

Cohen was sentenced to three years in prison in December 2018, after pleading guilty to violating federal campaign finance law in connection with hush-money payments and lying to Congress, among other crimes.

During Friday's interview on "GMA," Cohen said he followed Trump's "message" for more than a decade and "that is what got me in trouble."

When asked if he feels ready to be cross-examined, Cohen replied: "Absolutely."

"The documents will speak for themselves," he added, referring to the sealed indictment.

"So, not just your testimony?" Stephanopoulos responded.

"No," Cohen said. "And it's also corroborating testimony, but it's documents."