The White House confirmed late Friday that the extremist group calling itself the Islamic State is holding former US Army Ranger Peter Kassig hostage.

The group, which is also known as ISIS or ISIL, threatened Kassig at the end of a video purporting to show the execution of British aid worker Alan Henning.

“We can confirm that U.S. citizen Peter Kassig is being held by ISIL,” said Caitlin Hayden, a spokesman for the White House’s national security council.

“At this point we have no reason to doubt the authenticity of the video released earlier today. We will continue to use every tool at our disposal — military, diplomatic, law enforcement and intelligence — to try to bring Peter home to his family.