After months of silence from the captors of American journalist James Foley, his family received a chilling message on the night of Aug. 13: Foley would be executed in retaliation for U.S. airstrikes on the militant group Islamic State.

The family passed the message on to the U.S. government. The Federal Bureau of Investigation, which handles cases involving kidnapped American citizens, helped craft a response, pleading for mercy, said Phil Balboni, chief executive of GlobalPost, the Boston-based online news publication that employed Foley.

"It was an appeal for mercy. It was a statement that Jim was an innocent journalist" who respected the people of Syria, where he was held, Balboni said in a telephone interview.