The father of two children went to war-torn Syria to try to help struggling civilians at a refugee camp.
But he ended up a political pawn in the hands of brutal jihadists, becoming the third Western hostage beheaded by ISIS in a matter of weeks.
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Alan Henning with an ISIS member in a frame taken from a video released by ISIS.
Alan Henning with an ISIS member in a frame taken from a video released by ISIS.
And once again, the terrorist group is threatening to kill yet another of its high-profile captives.
The gruesome video showing the death of British aid worker David Haines prompted revulsion and condemnation after it was posted Saturday.
"The murder of David Haines is an act of pure evil," British Prime Minister David Cameron said on Twitter.
"We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes," he vowed.
Britain's top security and intelligence officials will hold an emergency meeting Sunday to discuss the crisis as the life of another British man held by ISIS hangs in the balance.
The video of Haines' death shows a masked ISIS militant placing his hand on another captive, whom he identified as Alan Henning, a British citizen.