The parents of James Foley, the American journalist beheaded by Islamist militant kidnappers, released on Thursday an email from his captors, dated Aug. 12, in which the militants proclaimed with strident bombast that he would be the first of many Americans to die.

GlobalPost, the news website that had employed Mr. Foley and helped his parents seek his release for the past two years, published the full text of the email from the Islamic State in Iraq and Syria, which called it “a message to the American government and their sheep-like citizens.”

The email, interspersed with sentences in all capital letters or italics, exclamation points for emphasis and a few misspellings, offered the first confirmation from ISIS that it had wanted a ransom or prisoner swaps for Mr. Foley and other American hostages. “You were given many chances to negotiate the release of your people via cash transactions as other governments have accepted,” the letter read.

GlobalPost said, however, that the family had heard nothing from the captors for more than a year before receiving a demand for a ransom of 100 million euros, or about $132 million.