Without a face to study in the graphic video of Foley’s murder, officials are analyzing the voice recording, other videos, statements and social-media postings for clues to the man’s identity, said Todd Hinnen, a former national security official at the U.S. Justice Department.

Attorney General Eric Holder today said the department’s national security division is heavily engaged in pursuing a criminal investigation.

“Those who would perpetrate such acts need to understand something: This Justice Department, this Department of Defense, this nation, we have long memories, and our reach is very wide,” Holder said. “We will not forget what happened, and people will be held accountable, one way or the other.”