Sotloff fixer Yosef Abobaker says U.S. authorities never interviewed him about ISIS . FBI says it ` ` is actively investigating the savage murder of Steven Sotloff '' Abobaker says masked ISIS fighters surrounded him , two , three armed guards . FBI believes a border guard informed ISIS about Sotloff 's location .
Sotloff fixer Yosef Abobaker says U.S. officials never interviewed him about ISIS . FBI says it `` is actively investigating the savage murder of Steven Sotloff '' Abobaker says masked ISIS gunmen outnumbered him , Sotloff , three armed guards . Abobaker believes a border guard informed ISIS about Sotloff 's location .