The Islamic State in Iraq and Syria released a video on Saturday that showed what appeared to be the beheading of a British citizen, David Cawthorne Haines, an aid worker.

He is seen kneeling on a bare hill in a landscape that appears identical to the one where two American journalists were killed by the group in back-to-back-executions in the past month, according to the footage and a transcript released by SITE Intelligence, which tracks the terrorist group.

In the moments before his death, Mr. Haines, 44, as the two slain journalists before him did, reads a script in which he blames his country’s leaders for his killing. Addressing Prime Minister David Cameron of Britain, he says, “You entered voluntarily into a coalition with the United States against the Islamic State, just as your predecessor Tony Blair did, following a trend among our British prime ministers who can’t find the courage to say no to the Americans.”