The Islamic State jihadist group claims to have executed American photojournalist James Foley, who was missing from Syria for nearly two years.

The White House says it is working to confirm whether the video is authentic.

But in a message posted to the Facebook page of the official campaign to free Foley, his mother, Diane Foley, was already mourning the loss of her oldest child.

“We have never been prouder of our son Jim. He gave his life trying to expose the world to the suffering of the Syrian people,” the post read. “We thank Jim for all the joy he gave us. He was an extraordinary son, brother, journalist and person.”

Diane Foley implored the militants to spare the lives of other hostages, who she argued have no control over the actions or policy of the U.S. government.

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Foley, 40, was kidnapped by an “organized gang” on Nov. 22, 2012 as he left an Internet café in Binesh, Syria, according to the official report on his disappearance from the FBI. He was on assignment for Boston-based international news site GlobalPost at the time.

A video viewed by the Star titled, “Message to America,” purports to be the product of the Islamic State militant group and shows a man in orange clothing kneeling next to a man in black garb, whose face is covered.

The captive man addresses his parents and brother before the man in black denounces the U.S. government and pulls a knife across the captive’s neck. A photo of a decapitated body then flashes on the screen.

The Star cannot independently confirm the authenticity of the video.

YouTube has since removed the video, citing its policy on violent content.

“If genuine, we are appalled by the brutal murder of an innocent American journalist, and we express our deepest condolences to his family and friends,” said U.S. National Security Council spokesperson Caitlin Hayden in a statement.

News of the video’s existence first spread on social media early Tuesday evening, prompting shock and outcries from fellow journalists — including those who worked with Foley on the ground. Many pleaded for the video and graphic images not to be shared.

The official campaign to Free James Foley, which shares messages said to be on behalf of the Foley family, posted words of caution Tuesday evening.

“We know that many of you are looking for confirmation or answers. Please be patient until we all have more information, and keep the Foleys in your thoughts and prayers,” a Facebook post read.

GlobalPost, which says it has mounted an “extensive international investigation” to find Foley, also reiterated the video has not yet been verified. CEO Philip Balboni said the FBI is involved in those efforts.

GlobalPost, for whom Foley had reported in Syria, said significant research has been undertaken throughout the Middle East, including along the Syria-Turkey border, in Lebanon, in Jordan and in other locations.

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“Although GlobalPost’s investigation at one point led us to believe that James was being held by the Syrian government, we later were given strong reason to believe he was being held by Islamic militants in Syria,” Balboni said. “We withheld this information at the request of the family and on the advice of authorities co-operating in the effort to protect Jim. GlobalPost, working with a private security company, has amassed an enormous amount of information that has not been made public.”

Speaking on behalf of Foley’s parents, Balboni said in a statement on the news site that he can’t comment further until they hear more from officials.

“We ask for your prayers for Jim and his family,” he said.

Foley, a New Hampshire native, is the oldest of five siblings and worked as a teacher before attending Northwestern University in Chicago to study journalism. He graduated in 2008 and has since been working as a freelance journalist.

The video showing the apparent execution begins with a clip of U.S. President Barack Obama announcing the authorization of airstrikes in northern Iraq on Aug. 7. Obama detailed action against Islamic State convoys following what he called terrorist advances by the group towards Irbil, where American officials are stationed.

In the video, the man in orange reads from what appears to be a prepared statement and condemns the U.S. for the attacks.

He speaks of his “beloved parents” and requests they not receive any compensation from the government and his brother, “John,” a member of the U.S. air force, to “think about who made the decision to bomb Iraq recently.”

“I died that day, John. When your colleagues dropped that bomb on those people they signed my death certificate,” the man says.

The man in black, speaking in what sounds like a British accent and holding a short blade, blames the death on U.S. military action and claims another captured freelance journalist, Steven Sotloff of Miami, is next, while holding a second man by the collar of his shirt.

“Any attempt by you, Obama, to deny the Muslims their right of living in safety under the Islamic caliphate will result in the bloodshed of your people,” the masked man says.

Foley was also taken captive for 44 days in Libya under Moammar Gadhafi’s rule. He wrote at length about the experience for GlobalPost.

The journalist championed getting close to conflict on the ground to better understand the world.

“I believe that front line journalism is important,” he told the Boston Globe in 2011, following his capture in Libya. “Without these photos and videos and firsthand experience we can’t really tell the world how bad it might be.”

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