ISIL militants beheaded British aid worker Alan Henning in a video posted Friday, triggering swift condemnation by the British and U.S. governments

ISIL militants beheaded British aid worker Alan Henning in a video posted Friday, triggering swift condemnation by the British and U.S. governments.

The footage on YouTube, highlighted on pro- ISIL Twitter feeds, showed a middle-aged man in an orange jumpsuit kneeling next to a black-clad militant in arid scrubland, similar to past ISIL beheading videos of two American journalists and a British aid worker.

As in previous videos, Henning appears to read from a script before he is killed. "Because of our parliament's decision to attack the Islamic State, I, as a member of the British public, will now pay the price for that decision," he says.

A male voice with a British accent says, "The blood of David Haines was on your hands Cameron," in references to the slain aid worker and to Britain's prime minister. " Alan Henning will also be slaughtered, but his blood is on the hands of the British parliament."

Henning, a 47-year-old taxi driver from Salford in northern England, was part of an aid convoy taking medical supplies to a hospital in northwest Syria in December last year when it was stopped by gunmen and he was abducted.

In response to the video, Cameron said: "The brutal murder of Alan Henning by ISIL [IS] shows just how barbaric and repulsive these terrorists are. My thoughts and prayers tonight are with Alan's wife Barbara, their children and all those who loved him.

"Alan had gone to Syria to help get aid to people of all faiths in their hour of need. We will do all we can to hunt down these murderers and bring them to justice."

U.S. officials said they had no reason to doubt the authenticity of the video, titled "Another Message to America and its Allies."

"The United States strongly condemns the brutal murder of United Kingdom citizen Alan Henning," President Barack Obama said in a statement.

"Standing together with our U.K. friends and allies, we will work to bring the perpetrators of Alan's murder - as well as the murders of Jim Foley, Steven Sotloff and David Haines - to justice," Obama said, referring to other captives killed by ISIL militants.

Near the end of the one-minute, 11-second video, the man in black introduces another hostage identified as American Peter Edward Kassig. His parents later issued a statement confirming their 26-year-old son had been taken captive while doing humanitarian work in Syria.

"We ask everyone around the world to pray for the Henning family, for our son, and for the release of all innocent people being held hostage in the Middle East and around the globe," Ed and Paula Kassig of Indianapolis, Indiana, said in the statement.

Kassig had served in the U.S. Army during the Iraq war before being medically discharged, the family said. Pentagon records show he spent a year in the army as a Ranger and was deployed to Iraq from April to July 2007.