Attendees pray at a vigil for Abdul-Rahman Kassig, who last week was named the next beheading target of the Islamic State terror group, at Butler University, Wednesday, Oct. 8, 2014 in Indianapolis.

Attendees pray at a vigil for Abdul-Rahman Kassig, who last week was named the next beheading target of the Islamic State terror group, at Butler University, Wednesday, Oct. 8, 2014 in Indianapolis. AJ Mast/AP

ISIS Beheads Another American Hostage

A video released Sunday by the terrorist group shows the execution of an American aid worker and former U.S. Army Ranger. By Marina Koren

The Islamic State claims in a new video to have beheaded an American hostage in Syria, the Associated Press reported Sunday morning.

Abdul-Rahman Kassig, previously known as Peter, had traveled to the country on a humanitarian mission. He was captured by the terrorist group in October 2013. Kassig, a former U.S. Army Ranger, converted to Islam following his kidnapping. The Washington Post describes the 15-minute long video:

Standing over the young man's severed head, a militant with a British accent says in the Islamic State video: "This is Peter Edward Kassig, a U.S. citizen of your country. Peter, who fought against the Muslims in Iraq while serving as a soldier under the American army, doesn't have much to say."

The video doesn't depict the militant beheading Kassig.

The video shows a mass beheading of several Syrian soldiers, according to AP.

The militant who carries out Kassig's execution appears to be the same one who was in previous videos of beheadings released by the Islamic State, which says the deaths are in response to U.S. airstrikes in Syria. The group warned it would kill Kassig in an Oct. 3 video that showed the beheading of British aid worker Alan Henning.

The latest video did not show other Western captives or warn of future beheadings, AP reports.

U.S. intelligence is working to confirm the authenticity of the video. "If confirmed, we are appalled by the brutal murder of an innocent American aid worker and we express our deepest condolences to his family and friends," said National Security Council spokeswoman Bernadette Meehan on Sunday.

The Kassig family said in a Facebook post Sunday morning that they are aware of news reports of the video.

"The family respectfully asks that the news media avoid playing into the hostage takers' hands and refrain from publishing or broadcasting photographs or video distributed by the hostage takers," the statement read. "We prefer our son is written about and remembered for his important work and the love he shared with friends and family, not in the manner the hostage takers would use to manipulate Americans and further their cause."

Kassig is the fifth Western hostage to be killed by the Islamic State this year.