'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

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

Court papers in the trial of two cell members show authorities detained them on multiple occasions due to their radical activities, but released them every time

UK-born Alexanda Kotey admits to involvement in scheme to kidnap and torture Westerners, including Israeli-American Steven Sotloff, among four beheaded by group

Court documents show British citizen Alexanda Amon Kotey, whose cell murdered US-Israeli journalist Steven Sotloff and others, has a scheduled change of plea hearing

2 suspects, allegedly part of brutal Jihadi cell dubbed 'The Beatles,' are on trial in US for helping terror group carry out killings, hostage negotiations

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

President calls family of US-Israeli reporter Steven Sotloff after press conference on mission that brought death of Abu Bakr al-Baghdadi