President Donald Trump issued a sweeping series of pardons for defendants charged in the Jan. 6, 2021, attack on the U.S. Capitol, commuting the sentences of 14 individuals and offering a “a full, complete and unconditional pardon to all other individuals convicted of offenses related to events that occurred at or near the United States Capitol on January 6, 2021."

"So, this is January 6th. These are the hostages, approximately 1,500 for a pardon," Trump said while holding the black folder containing the order.

The 14 individuals that Trump identified that he was commuting sentences for are those convicted or otherwise charged with engaging in the separate seditious conspiracies mounted by leaders of the Proud Boys and Oath Keepers to thwart the lawful transfer of power on Jan. 6, 2021. They were among the more grave and high profile charges brought in connection with January 6.

Former Proud Boys leader Enrique Tarrio, who was sentenced to 22 years in prison after his conviction of seditious conspiracy, was being processed for release from his cell in Louisiana following Trump’s executive action, his lawyer told ABC News Monday evening.

Tarrio was notably sentenced to the longest term of imprisonment among all of the nearly 1,600 individuals charged in connection with the attack.

Outside the Central Detention Facility in Washington, crowds of supporters of those inside sang the national anthem with rioters over the phone. One person could be heard saying, "Thank you, President Trump! We're getting out tonight."

Former House Speaker Nancy Pelosi, who was among the lawmakers who were rushed from the House and Senate chambers and offices after rioters breached the Capitol, called Trump's order "shameful."

"The President's actions are an outrageous insult to our justice system and the heroes who suffered physical scars and emotional trauma as they protected the Capitol, the Congress and the Constitution," Pelosi said.

Craig Sicknick, whose brother Capitol Police officer Brian Sicknick died the day after being attacked by rioters, told ABC News' Rachel Scott that Trump's pardons were a "betrayal of decency."

"The man doesn't understand pain or suffering of others. He can't comprehend anyone else's feelings," Sicknick said. "We now have no rule of law."

Brian Sicknick suffered two strokes after the riot. A D.C. medical examiner said he died of natural causes, but "all that transpired on that day played a role in his condition."

Trump was expected to further direct the incoming attorney general to move to dismiss all pending indictments against Jan. 6 defendants who have not yet had their cases fully adjudicated, which would shutter roughly 470 ongoing cases, according to recently released numbers by the District of Columbia U.S. Attorney's Office.

Current and former DOJ officials have expressed alarm over the potential that Trump would hand down pardons -- or otherwise free -- violent offenders, citing the potential risk they could seek to target the prosecutors who oversaw their cases, the judges who sentenced them to periods of incarceration, or witnesses who may have testified against them.

Trump teased the pardons earlier Monday at Capital One Arena, where he spoke to supporters after taking the oath of office at the Capitol.

A violent mob of pro-Trump protesters stormed the Capitol on Jan. 6, fighting with officers, breaking into offices and destroying property.

After the attack on the U.S. Capitol by rioters seeking to overturn the 2020 election, more than 1,580 people were charged criminally in federal court, according to the Department of Justice. More than 1,000 have pleaded guilty.

Trump's team had drafted a list of potential pardons for Jan. 6 defendants to issue on Day 1, sources familiar with the matter told ABC News on Sunday.

Of the nearly 1,600 individuals who have faced charges associated with the Capitol attack, according to figures released by the U.S. Attorney's Office, 608 individuals faced charges for assaulting, resisting or interfering with law enforcement trying to protect the complex that day, the office said. Approximately 140 law enforcement officers were injured during the riot, the DOJ has said.

The U.S. Attorney's Office said it was evaluating whether to bring charges in roughly 200 cases that were referred to them by the FBI, about 60 of which involve potential felony charges involving allegations of assault or impeding law enforcement.

Trump said last March that he was "inclined to pardon many" of the rioters.

At least 221 individuals were found guilty at contested trials in U.S. District Court, the DOJ said. Another 40 individuals were convicted following an agreed-upon set of facts presented to and accepted by the Court.

Outgoing President Joe Biden on Monday issued preemptive pardons to potential targets of the incoming Trump administration, including lawmakers who served on the House Jan. 6 Committee.

Trump, in his 2024 campaign, repeatedly vowed "retribution" on his political enemies, specifically singling out lawmakers like Liz Cheney, who investigated the attack on the Capitol. Trump said Cheney and other committee members should be put in jail.

ABC News' Lalee Ibssa, Michelle Stoddart and Meredith Deliso contributed to this report.