(CBS/CNN) — Two high-profile ISIS fighters have been indicted on terrorism charges related to the hostage-taking and deaths of four Americans, including slain New Hampshire journalist James Foley, the US government announced Wednesday.

Alexanda Kotey and El Shafee Elsheikh, who were part of an ISIS execution cell dubbed “the Beatles” because of their British accents, are expected to make their initial appearances in federal court in Alexandria, Virginia Wednesday afternoon. They are in FBI custody.

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Kotey and Elsheikh are charged for their involvement in the hostage-taking and murders of American journalists Foley and Steven Sotloff and American aid workers Peter Kassig and Kayla Mueller as well as British and Japanese nationals.

Foley was kidnapped in northern Syria in 2012 and his beheading two years later was captured on video and spread on the internet by ISIS.

According to the indictment, they are charged with one count of conspiracy to commit hostage-taking resulting in death, four counts of hostage-taking resulting in death, one count of conspiracy to murder US citizens outside of the US, one count of conspiracy to provide material support to terrorists — hostage-taking and murder — resulting in death, one count of conspiracy to provide material support to a designated foreign terrorist organization resulting in death.

“Today is a good day, but it is also a solemn day,” Assistant Attorney General for National Security John Demers said at a press conference Wednesday. “Today we remember the four innocent Americans whose lives were taken by ISIS: James Wright Foley, Steven Joel Sotloff, Peter Edward Kassig, and Kayla Jean Mueller.”

“Many around the world are familiar with the barbaric circumstances of their deaths. But we will not remember these Americans for the way they died. We will remember them for the way they lived their good and decent lives.”

In a joint statement Wednesday released by the Foley Foundation, the families welcomed the news.

“James, Peter, Kayla and Steven were kidnapped, tortured, beaten, starved, and murdered by members of the Islamic State in Syria. Now our families can pursue accountability for these crimes against our children in a U.S. court,” they said.

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“Kotey and ElSheikh’s extradition and trial in the United States will be the first step in the pursuit of justice for the alleged horrific human rights crimes against these four young Americans, who saw the suffering of the Syrian people and wanted to help, whether by providing humanitarian aid or by telling the world about the evolving Syrian crisis.”

“We are hopeful that the U.S. government will finally be able to send the important message that if you harm Americans, you will never escape justice. And when you are caught, you will face the full power of American law,” the Foleys, Sotloffs, Kassigs and Muellers said.

Sen. Jeanne Shaheen, of New Hampshire, said in a statement “the United States has an opportunity to deliver real justice.”

“The families of James Foley, Peter Kassig, Steven Sotloff and Kayla Mueller have waited a long time for this – today is a giant step towards justice,” Shaheen said. “These terrorists have been in legal limbo for years but thankfully that ambiguity is now over. The families of the Americans murdered by ISIS finally have their day in court on the horizon.”

Elsheikh and Kotey had their British citizenships revoked for being considered a national security threat after joining ISIS in Syria. They had been held in US custody in Iraq.

Attorney General William Barr negotiated with Britain to extradite the pair to the US for prosecution by taking the death penalty off the table as consideration for sentencing.

“These charges are the product of many years of hard work in pursuit of justice for our citizens slain by ISIS. Although we cannot bring them back, we can and will seek justice for them, their families, and for all Americans,” Barr said in a news release.

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(© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. CNN’s Jennifer Hansler and Christina Carrega contributed to this report.)