The U.S. believes it has identified the British-accented masked man in the videos depicting the beheadings of two American journalists and a British aid worker, the FBI director says.
FBI Director James Comey told reporters at the bureau's headquarters he would not reveal the man's name or nationality.
Comey did not address whether the U.S. believes the man actually carried out the killings himself. The beheadings are not shown in the videos.
In the three videos, the man speaks British-accented English. He holds a long knife and appears to begin cutting the three men, American reporters James Foley and Steven Sotloff and British aid worker David Haines.
In late August, British Ambassador Peter Westmacott said his country was close to identifying the Islamic State group militant.