By Andrew Katz
October 3, 2014

Updated Saturday, Oct. 4

A video released Friday by the militant group Islamic State of Iraq and Greater Syria (ISIS) appears to show the execution of British aid worker Alan Henning. A man identified as Peter Edward Kassig, an American, is then threatened with a similar fate.

U.S. intelligence officials had not yet authenticated the video Friday evening, but it follows the pattern of other execution videos released by ISIS. “The brutal murder of Alan Henning by [ISIS] shows just how barbaric these terrorists are,” British Prime Minister David Cameron wrote on Twitter. “My thoughts are with his wife and their children.”

The White House also released a statement:

Henning, 47, was thought to have been abducted in Syria last December, shortly after crossing the border from Turkey in an aid convoy. Henning’s wife and family released the following statement Saturday morning:

Kassig, a former Army Ranger who deployed to Iraq in 2007, spoke with TIME in January 2013 about his humanitarian work and beginning an aid group called Special Emergency Response and Assistance.

Kassig’s family released this video statement Saturday morning:

Contact us at editors@time.com.

Read More From TIME

EDIT POST