WASHINGTON (CNN) -- A recent attempt to rescue American James Foley and others in Syria failed, a U.S. official told CNN on Wednesday, a revelation that came as new details emerged about the journalist's final days in the hands of ISIS militants.
The U.S. Department of Defense confirmed a rescue attempt was carried out this summer in Syria, but did not say whether Foley was among those U.S. officials had hoped to free.
"Unfortunately, the mission was not successful because the hostages were not present at the targeted location," Pentagon spokesman Rear Adm. John Kirby said.
But the U.S. official, speaking on condition of anonymity, said the mission was to free Foley and other American hostages.
The news broke a day after ISIS released a grisly video that showed Foley being beheaded and warned a second American journalist would be killed if the United States did not end its military operations in Iraq.
Hours earlier on Wednesday, it was revealed that Foley's family was told a week ago in an e-mail sent by his captors that the journalist would be executed.
"The message was vitriolic and filled with rage against the United States. It was deadly serious," said Philip Balboni, CEO of the online publication GlobalPost, which employed Foley.
"Obviously, we hoped and prayed that would not be the case ... Sadly, they showed no mercy."
In the video, which CNN is not showing, Foley is seen on his knees as a man cloaked in black -- his face covered -- stands behind him.
Foley is then executed.
The video of his killing also shows another U.S. journalist, believed to be Steven Sotloff. The militant in the video, who speaks English with what sounds like a British accent, says the other American's life hangs in the balance, depending on what President Barack Obama does next in Iraq.
Source: Foley was held in Aleppo
Foley, a freelance journalist, was on assignment for GlobalPost when he disappeared on November 22, 2012, in northwest Syria, near the border with Turkey.
ISIS, the militant group seeking an Islamic caliphate stretching from Iraq into Syria, has claimed credit and U.S. intelligence said the video is real.
A source who claims to have been held last year with Foley told CNN's Bharati Naik that he, Foley and another journalist were held from March to August 2013 in a prison in the Syrian city of Aleppo near Masha al-Adfaa hospital.
At the time, the source -- who spoke on condition of anonymity -- said they were being held by al-Nusra Front, a Syrian rebel group with ties to al Qaeda in Iraq.
At one point, according to the source, there were almost 100 people -- including other European journalists -- in the prison.
The source believes Foley and the other journalist, who was not Sotloff, were transferred to an ISIS training camp.
Foley and the other journalist, according to the source, were tortured in prison -- mostly beaten.
Foley and the other journalist, who the source declined to identify, said they gave him contact numbers and e-mail addresses to pass on message to their family members.
The source told CNN he lost the contacts and did not get in touch with the families. He says he did, however, give the information about the journalists to Western government authorities in November 2013, including details about where Foley was being held.
Messages from Foley's captors began last fall, Balboni of GlobalPost said.
"The captors never messaged a lot. There was a very limited number with a very specific purpose ... They made demands," he said.
Some messages were political, and some were financial, Balboni said.
Then came the message sent to Foley's family last week. "There was no demand," he said.
Foley's family, according to Balboni, responded in an e-mail, pleading for mercy and asking for more time.
They never heard back.
"Jim Foley was an incredibly brave journalist and an incredibly brave man, right to the horrible end of his life. We are devastated by his loss," Balboni told reporters.
'Jim was innocent'
In the video posted on YouTube, Foley reads a message, presumably scripted by his captors, that his "real killer'' is America.
"I wish I had more time. I wish I could have the hope for freedom to see my family once again," he can be heard saying in the video.
Foley's parents, flanked by one of his brothers, talked to reporters about their son's plight.
"Jim was innocent and they knew it," Diane Foley said. "They knew that Jim was just a symbol of our country."
His father, John, broke down several times.
"We beg compassion and mercy" for those believed to be holding the other American journalist shown in the video. Sotloff, a contributor to Time and Foreign Policy magazines, was kidnapped at the Syria-Turkey border in 2013.
"They never hurt anybody," John Foley said. "They were trying to help. There is no reason for their slaughter."
Foley previously had been taken captive in Libya. He was detained there in April 2011 along with three other reporters, and released six weeks later.
Afterward, he said that what saddened him most was knowing that he was causing his family to worry.
His parents talked about asking him why he wanted to return to conflict zones.
"Why do firemen keep going back to blazing homes?" John Foley told reporters. "This was his passion. He was not crazy. He was motivated by what he thought was doing the right thing ... that gave him energy to continue despite the risk."
His mother said she remembered him telling her, "Mom, I found my passion, I found my vocation."
Foley, 40, grew up in New Hampshire and graduated from Northwestern University's Medill School of Journalism in 2008.
Like some other young journalists working after the September 11 terror attacks, Foley was drawn to Iraq, Afghanistan and other areas of conflict.
Friends described Foley as fair, curious and impressively even-tempered.
"Everybody, everywhere, takes a liking to Jim as soon as they meet him," journalist Clare Morgana Gillis wrote in a blog post about him in May 2013, six months after he disappeared in Syria.
"Men like him for his good humor and tendency to address everyone as 'bro' or 'homie' or 'dude' after the first handshake. Women like him for his broad smile, broad shoulders, and because, well, women just like him."
Searching for clues
U.S. and British counterterrorism analysts are examining every frame and piece of audio of the video for clues about where it took place and who the executioner is, U.S. officials, speaking on condition of anonymity, told CNN.
The voice in the video seems to have a British accent so they're trying to match any individuals known to the British government who may have gone to Syria to fight in that nation's civil war.
The analysts are looking at clothing, climate, terrain, language and wording and whether there are any National Security Agency or UK phone intercepts matching the voice, the officials said.
French journalist Nicolas Henin told France Info radio he had been held with Foley in northern Syria prior to his release in April.
Henin, who has never before spoken about Foley because he didn't want to jeopardize him, said he was held for seven months with the American journalist.
Hostages were held in groups. At one point, he shared a cell with Foley.
Foley "was in a difficult state," said Henin. "He already suffered a lot during his first months (of captivity) and thankfully we shared a phase (in our detention) that was less difficult."
Foley, according to Henin, said he had been initially kidnapped by a group of jihadists who were fighting in Syria.
The Committee to Protect Journalists estimates there are about 20 journalists missing in Syria, many of them held by ISIS.
Among them is American Austin Tice, a freelance journalist who was contributing articles to The Washington Post. Tice disappeared in Syria in August 2012. There has been no word of from him since his abduction.
Previous brutal killings of Americans
Foley's killing recalled the murder of Daniel Pearl, The Wall Street Journal correspondent who was kidnapped while reporting in Pakistan in January 2002. His killing was captured on video and posted online by al Qaeda.
Pearl's mother, Ruth Pearl, responded to Foley's death with a tweet posted by the Daniel Pearl Foundation Twitter account that reads: "Our hearts go out to the family of journalist James Foley. We know the horror they are going through."
Foley's death also harkened to the videotaped beheadings of Americans Nicholas Berg, Eugene Armstrong and Jack Hensley carried out by al Qaeda during the height of the Iraq War.
Barbara Starr reported from Washington, and Chelsea J. Carter reported and wrote from Atlanta. CNN's Evan Perez, Ashley Fantz, Dana Ford, Raja Razek, Kevin Liptak, Jethro Mullen, Elise Labott and Leslie Bentz contributed to this report.
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