The video shows Haines, who was captured by militants in Syria in 2013, wearing an orange jumpsuit and kneeling in the desert while he reads from a prepared script.
It later shows what appears to be the aid worker’s body. The Foreign Office in a statement said, “All the signs are that the video is genuine.”
Like with previous IS murder videos showing the beheading of US journalists James Foley and Steven Sotloff, it ends with a threat to kill another hostage -- a second British national.
The emergence of the footage late Saturday night saw Prime Minister David Cameron return to Downing Street after midnight. He has since chaired a meeting of the government’s emergency committee Cobra, and issued a statement afterwards saying that the killing would not change Britain’s strategy against the IS.
Speaking from Downing Street on Sunday morning, the PM condemned Haines’ killers and said the UK would “hunt down those responsible and bring them to justice, no matter how long it takes”, adding, “They are not Muslims, they are monsters.”
He described Haines, 44, as a “British hero”, and praised the “extraordinary courage” of his family. But while he said that “we have to confront this menace,” Cameron added that this will not involve direct British involvement in fighting.
The UK is instead playing a supporting role to the US, providing transport and supplies.
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