The Islamic State terrorist group says it has executed British aid worker David Cawthorne Haines.

The group released a two and a half minute video purportedly showing Haines being beheaded. Haines, a 44-year-old father of two, was kidnapped last year just three days after he arrived in Syria to work for an international relief agency.

The execution video, entitled “A Message to America’s Allies,” emerged shortly after Haines’ family issued a public plea for his captors to contact them. In it, his hooded executioner blames British Prime Minister David Cameron for joining forces with the United States against the Islamic State. The executioner warned that the decision will drag the British people into “another bloody and unwinnable war.” At the end of the video, the group threatens to behead another British hostage.

Cameron issued a message on Twitter moments after the video was released, calling the murder of David Haines “an act of pure evil.” He expressed condolences to Haines’ family members who, he said “have shown extraordinary courage and fortitude.” Cameron said his government will “do everything in our power to hunt down these murderers and ensure they face justice, however long it takes.”

British media reported that the prime minister is heading to his office to chair a COBRA (British national emergency committee) meeting to decide on how to proceed.

In Washington, the White House issued a statement by President Barack Obama condemning the murder as barbaric. Obama said the U.S. “stands shoulder to shoulder tonight with our close friend and ally in grief and resolve.” The president pledged to “work with the United Kingdom and a broad coalition of nations from the region and around the world to bring the perpetrators of this outrageous act to justice, and to degrade and destroy this threat to the people of our countries, the region and the world.”

Islamic State militants have beheaded American journalists Jim Foley and Steven Sotloff in recent weeks. The terrorist group said the Americans were killed in retaliation for U.S. strikes on their positions in Iraq. The militants also have beheaded Lebanese and Kurdish opponents.

Kurdish and Iraqi forces with heavy American air support wrested from the terror group control of the strategic Mosul Dam last month.

Haines was kidnapped in March of 2013 while working for the France-based ACTED (Agency for Technical Cooperation and Development). The group published a statement about the gruesome execution on its web site shortly after the footage surfaced.

We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes.

— David Cameron (@David_Cameron) September 13, 2014

The murder of David Haines is an act of pure evil. My heart goes out to his family who have shown extraordinary courage and fortitude.

— David Cameron (@David_Cameron) September 13, 2014

Some information for this report comes from Reuters.
…