LONDON -- The mother of slain hostage James Foley said Friday that she wants two British men who were part of the Islamic State of Iraq and Syria (ISIS) cell that killed her son to be tried and imprisoned for the rest of their lives. Diane Foley welcomed the capture of the men who were part of a group, all of whom had lived in London, known as "The Beatles" because of their British accents.

Foley told the BBC on Friday that the arrests announced Thursday won't bring her son back, but "hopefully it protects others from this kind of crime."

She said "their crimes are beyond imagination. They really have not done anything good in the world, so I think they need to spend the rest of their life being held."

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James Foley was killed on Aug. 19, 2014, after being held hostage for several months.

U.S. officials confirmed this week that the American-backed Syrian Democratic Forces (SDF) had captured the two notorious members of the ISIS insurgent cell commonly dubbed "The Beatles," which was known for beheading hostages.

Air Force Col. John Thomas said that El Shafee Elsheikh and Alexanda Amon Kotey were captured in early January in eastern Syria. The two men, both from west London, are among four members of the ISIS cell that captured, tortured and beheaded more than two dozen hostages including American journalists Foley and Steven Sotloff, and American aid worker Peter Kassig.

The State Department has imposed sanctions on both men. They are believed to be linked to the British terrorist known as Jihadi John, the masked ISIS militant who appeared in several videos depicting the graphic beheadings of Western hostages. In addition to the Americans, Emwazi was seen in videos showing the murders of British aid workers David Haines and Alan Henning, Japanese journalist Kenji Goto and a number of other ISIS hostages.

Thomas, a spokesman for U.S. Central Command, said American officials have been able to interrogate the two detainees. And he characterized their capture as "certainly a big deal for America" as well as the families of the people the two men killed.

While the SDF discovered the two and captured them, the U.S. helped with biometric data and other tools to accurately identify them.

The U.S. has been training the SDF in border and internal security, including how to screen individuals and determine if they are foreign fighters or other enemies hiding in the population.

Their capture was first reported by the New York Times.

According to the U.S., Elsheikh traveled to Syria in 2012 and first joined al Qaeda's branch there, and then later joined ISIS. The State Department, in imposing sanctions on Kotey last year, said he likely engaged in executions and torture, including electronic shock and waterboarding, and recruited several British nationals to ISIS.

According to Thomas, the two men represent just a small portion of the hundreds of foreign-born ISIS terrorists from a number of nations that SDF fighters have captured or killed since October 2017.

He said that so far the future of the detainees is undetermined and it's not clear what the process will be for bringing them to justice.

U.S. officials did not provide any other details of the capture, but said the U.S. government works closely with its coalition partners on the disposition of detainees held by the SDF. They said those discussions are private and no additional information would be given.

Sotloff was kidnapped in August 2013 after crossing into Syria from Turkey. He was killed on Sept. 2, 2014, and a video was distributed around the world documenting his death.

Foley had been killed a month earlier by ISIS. Kassig was an American aid worker captured by the militants in 2013 while delivering relief supplies to refugees in Syria.