David Cameron emerged from an emergency meeting this morning with harsh words for Islamic State militants in the wake of yesterday's video that purports to show the beheading of British aid worker David Haines: Calling the execution—which hasn't been officially verified, though a UK Foreign Office rep tells the Wall Street Journal that "all signs are that the video is genuine"—"an act of pure evil," the BBC reports that Cameron vowed "we will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes." In the video, Haines singled out Cameron thusly: "I would like to declare that I hold you, David Cameron, entirely responsible for my execution." ISIS militants threatened a second British hostage, Alan Henning, with the same fate.
The White House issued a statement last night, as per the Journal, saying that President Obama "strongly condemns the barbaric murder of UK citizen David Haines," and that "Our hearts go out to the family of Mr. Haines and to the people of the United Kingdom." Haines' family, which the AP notes had asked ISIS to contact them, said in a statement that Haines' "joy and anticipation for the work he went to do in Syria is for myself and family the most important element of this whole sad affair." (Read more David Haines stories.)