A video posted online Tuesday purported to show the beheading of U.S. journalist Steven Sotloff by the Islamic State of Iraq and Syria(ISIS), just days after Sotloff's mother had pleaded for his release. The extremist group called it retribution for continued U.S. airstrikes in Iraq.
Sotloff, 31, who freelanced for Time and Foreign Policy magazines, had last been seen in Syrian in August 2013 until he appeared in a video released online last month by ISIS that showed the beheading of fellow American journalist James Foley.
Dressed in an orange jumpsuit against the backdrop of an arid Syrian landscape, Sotloff was threatened in that video with death unless the U.S. stopped airstrikes on the group in Iraq.
In the video distributed Tuesday and entitled "A Second Message to America," Sotloff appears in a similar jumpsuit before he was purportedly beheaded by an ISIS fighter.
CBS News could not immediately verify the video's authenticity. The SITE Intelligence Group, a U.S. terrorism watchdog, first reported about the video's existence.
In a two-sentence statement Tuesday, family spokesman Barak Barfi said Sotloff's family "knows of this horrific tragedy and is grieving privately."
In Washington, State Department spokeswoman Jen Psaki said U.S. intelligence analysis will "work as quickly as possible" to determine if the video of the beheading is authentic.
"If the video is genuine, we are sickened by this brutal act, taking the life of another innocent American citizen," Psaki said. "Our hearts go out to the Sotloff family and we will provide more information as it becomes available."
Psaki said it's believed that "a few" Americans are believed to still be held by ISIS but would not give any specifics.
The fighter who beheads Sotloff in the video called it retribution for Obama's continued airstrikes against the group in Iraq.
"I'm back, Obama, and I'm back because of your arrogant foreign policy towards the Islamic State ... despite our serious warnings," the fighter said. "So just as your missiles continue to strike our people, our knife will continue to strike the necks of your people."
Last week, Sotloff's mother issued a direct plea to the extremist group's leader to spare her son's life.
Addressing the leader of ISIS group by name, Shirley Sotloff said in a video her son was "an innocent journalist" who shouldn't pay for U.S. government actions in the Middle East over which he has no control.
A man who answered a phone listed in the name of Sotloff's sister hung up when called by the AP.
ISIS, which has taken over a third of Syria and Iraq, has terrorized rivals and civilians alike with widely publicized brutality as it seeks to expand a proto-state it has carved out on both sides of the border.
In its rise to prominence over the past year, the extremist group has frequently published graphic photos and gruesome videos of everything from bombings and beheadings to mass killings.