According to The Associated Press, an Islamic State (IS) video-clip released on Sunday (November 16) depicts militants beheading a dozen Syrian soldiers and ends with a militant claiming to have killed US aid worker Peter Kassig, 26, the latest slaughter proudly broadcast by the group on the Internet.
US officials said they were working to determine the video's authenticity. Kassig's family said it was awaiting the outcome of the investigation.
"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," the family said in a statement.
The Associated Press could not independently verify the footage, though it appeared on websites used in the past by the Islamic State group, which now controls a third of Syria and Iraq.
The video identifies the militants' location as Dabiq, a town in northern Syria that the militant group uses as the title of its English-language propaganda magazine and where they believe an apocalyptic battle between Muslims and their enemies will occur.
The high-definition video reveals the beheading of roughly a dozen Syrian military officers and pilots, all dressed in blue jumpsuits. The dominant IS militant in the video speaks to the camera in a British accent and warns US soldiers they will meet a similar fate.
The militant's voice is distorted in the video. Previous videos featured a militant with a British accent that the FBI says it has identified, though it hasn't named him publicly.
IS claims it beheaded Kassig, 26, because he "fought against the Muslims in Iraq while serving as a soldier." Peter Kassig, from Indianapolis, IN, served in the U.S. Army's 75th Ranger Regiment, a special operations unit, and deployed to Iraq in 2007.
After being medically discharged, Kassig formed the aid organization Special Emergency Response and Assistance (SERA), in Turkey to aid Syrian refugees. He delivered food and medical supplies and provided trauma care to wounded Syrian civilians before being captured in eastern Syria last year. Friends say he converted to Islam in captivity and took the first name Abdul-Rahman.
Burhan Agha, a Syrian friend who worked with Kassig in Lebanon and who moved to Switzerland seeking asylum, wept when recounting his generosity Sunday.
COMMENT: The White House said the US intelligence community was analyzing the video. National Security Council (NSC) spokeswoman Bernadette Meehan said that if the video is authentic, the White House would be "appalled by the brutal murder of an innocent American."
British Prime Minister David Cameron said he was "horrified by the cold-blooded murder," saying that IS has "again shown their depravity."
Previous videos have shown the beheading of two American journalists and two British aid workers. The latest video did not depict the person identified as Kassig being beheaded.
Unlike previous videos, it did not reveal other Western captives or directly threaten to behead anyone else. It also had lingering close-ups on some miltiants' exposed faces, with a few appearing to be foreigners.
IS holds British photojournalist John Cantlie, who has appeared in several videos delivering statements for the group, likely under duress. They also hold a 26-year-old American woman captured last year in Syria while working for aid groups. US officials have asked that the woman not be identified out of fears for her safety.
IS has beheaded and shot dead hundreds of captives--mainly Syrian and Iraqi soldiers--during its sweep across the two countries, and has celebrated its mass killings in extremely graphic videos.
On Sunday, IS claimed a bombing at the Baghdad International Airport that wounded five people, saying it was trying to strike Americans there. No one was wounded in a passing United Nations convoy, the organization said.