The Sunni militant group Islamic State is holding another American hostage. The revelation came in a video showing the beheading of British citizen Alan Henning.

At the end of the the video, a man warns that Peter Kassig, an Iraq War veteran, is next.

In a statement, Kassig's family confirmed that the 26-year-old was in Syria performing humanitarian work. National Security Council spokesperson Caitlin Hayden said the U.S. had no reason to "doubt the authenticity of the video released earlier today" and that the U.S. "will continue to use every tool at our disposal — military, diplomatic, law enforcement and intelligence — to try to bring Peter home to his family."

With that, here's what we know about Kassig:

• The Pentagon says Kassig served as an Army Ranger and was deployed to Iraq once.

• A spokesperson for the family says that after receiving an honorable discharge from the Army for medical reasons, he became an emergency medical technician.

• In 2012, he moved to Lebanon, where he worked to provide care to Palestinian refugees, and in the summer of 2013 he moved to Turkey, where he provided care for Syrian refugees.

• In October of 2013, he was working on a project in Syria for a humanitarian group he founded, Special Emergency Response and Assistance.

• He was on his way to Deir Ezzour, in eastern Syria, when he was captured.

• His family says that after his capture, Kassig converted to Islam and changed his first name to Abdul-Rahman.

"The family understands from speaking to former hostages that Kassig's faith has provided him comfort during his long captivity," the family spokesperson said.

In a 2012 profile on CNN, Kassig said he went to Lebanon because there's a sense that there's no hope in that area of the world.

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