'Hatred truly overwhelmed your humanity,' mother of 1 of El Shafee Elsheikh's victims says, after he's found guilty for role in 'vicious and sadistic' group that killed 4 Americans

British national El Shafee Elsheikh found guilty of belonging to group known for their cruelty to captives, including 4 Americans who were killed

El Shafee Elsheikh one of four UK members of IS cell believed behind killing of journalists James Foley and Steven Sotloff, aid workers Peter Kassig and Kayla Mueller

Canadian Mohammed Khalifa narrated videos as part of cell that filmed murders of James Foley and American-Israeli Steven Sotloff

Alexanda Kotey and El Shafee Elsheikh stand accused of belonging to a cell blamed for the jailing, torture and murder of Western hostages in Syria

Suspects are two of the four terrorists dubbed 'the Beatles, for their accents, accused of killing Western hostages, including Jewish American journalist Steven Sotloff

Two IS terrorists go on trial for the killing of US journalists James Foley and Steven Sotloff, and aid workers Peter Kassig and Kayla Mueller