The militant group Islamic State of Iraq and the Levant (ISIL or ISIS) released a video purportedly showing the execution of British hostage Alan Henning, which closes with a threat against Peter Edward Kassig, an American citizen who served with the U.S. Army Rangers.

A native of Indiana, Kassig, 26, was working to help Syrian refugees by providing medical and humanitarian support with a group he founded called Special Emergency Response and Assistance (SERA), according to Time.

On its website, the group says it had temporarily ceased operations “due to the present security situation in Syria.”

SERA was founded by Kassig in late 2012 along with his friend Eliot Stempf. According to an article from Reed College, the pair lived together in Turkey and frequently crossed over into Syria to help train locals to become emergency first responders.

Kassig joined the Army in 2006 and served as a Ranger, but was honorably discharged for medical reasons after his deployment to Iraq in 2007, according to CNN. He went on to college and became certified as an emergency medical technician in 2010.

In an interview with the website Syria Deeply last year, Kassig said he was adamant about only providing humanitarian, and not military support.

“I can either be in a position to deliver tens of thousands of dollars of antibiotics for women and children, or I can be another young man with a gun,” he said.

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