SYRIA - ISIS has done it again.
The terrorist group released a video showing the apparent beheading of British aid worker Alan Henning.
In the video, Henning speaks to the camera about Britain's decision to join the bombing campaign against ISIS.
Henning was a taxi driver who went to Syria to help victims of war.
He was kidnapped last December.
British Prime Minister David Cameron reacted to the news on Twitter, calling the terrorists 'barbaric' and vowing to hunt them down and bring them to justice.
A memorial service was held at a mosque in Henning's home town of Manchester.
"The killing of Alan Henning was a cowardly and criminal act of appalling brutality by a group who do not represent Islam at all, and are, in fact, an insolent to the Islamic faith," said Imam Asim Hussain, of Manchester Central Mosque.
Despite an intense bombing campaign, ISIS is showing no signs of slowing down.
The latest video ends with yet another threat to another hostage - American aid worker Peter Kassig.
The 26-year-old served in the U.S. Army in Iraq.
After his honorable discharge, he set his sights on helping.
"There's this impression, this belief that there is no hope. That's when it's more important than ever that we come in, against all odds, and try to do something," Kassig said in a 2012 interview.
Kassig founded SERA, the non-profit Special Emergency Response and Assistance group, which was providing humanitarian aid to refugees fleeing the Syrian civil war.
He converted to Islam, but was kidnapped on October first of last year.
His parents released a YouTube video asking his captors to show mercy on their son, now known as Abdul-Rahman.
"Most of all, know that we love you, and our hearts ache for you to be granted your freedom," said Peter's mother, Paula Kassig.
Now, all they can do it wait to find out if those pleas fall on deaf ears.