The parents of James Foley, the American photojournalist whose horrific beheading by Islamic militants was shown on a YouTube video Tuesday night, called their son a hero and an inspiration who "didn't deserve to be slaughtered" in an emotional news conference Wednesday.

“He was an inspiration for us and so many others," said John Foley, his eyes tearing and his voice catching. "We miss his courage, his love, his determination, his laugh and his smile.”

Foley, a New Hampshire-born journalist who specialized in chronicling life in the world's most dangerous places, disappeared in northern Syria in November 2012 while freelancing for Agence France-Presse and the Boston-based media company GlobalPost. Foley, who had previosuly worked in Afghanistan for Stars and Stripes, was not seen or heard from again until the shocking and brutal video, in which his executioner blamed U.S. air strikes on the Islamic State in Iraq, surfaced.

Foley had been kidnapped previously in Libya, but had been freed and then returned to the craft he loved.

"This was his passion," John Foley said.

His mother called for compassion from her son's killers, who are holding another American journalist, Steven Sotloff, who they have also threatened to kill.

“Jim’s death can bring our country together in a stronger way in the values that Jim held dear,” said Diane Foley, who spoke with her husband from their home in the Granite State. “He never wanted us to hate or be bitter.”

U.S. intelligence officials were analyzing Wednesday a video released by Islamic militants showing the beheading of American journalist James Foley, focusing on identifying the surrounding landscape and the British accent of his executioner.

The identification of his killer is said to be of top importance to U.S. and European intelligence officials.

The video -- originally posted by ISIS to YouTube, which later took the video down -- also shows an ISIS militant standing over a second man dressed similarly to Foley in an orange jumpsuit. The video identifies the second man as American journalist Steven Sotloff, and warns that he, too, could be killed. Sotloff was kidnapped near the Syrian-Turkish border in August 2013, and freelanced for Time, the National Interest and MediaLine.

White House National Security Council spokeswoman Caitlin Hayden confirmed the video’s authenticity Wednesday. U.S. officials who asked not to be identified earlier told Fox News that the man beheaded in the video is Foley.

The orange jumpsuits worn by both captives in the video are synonymous in Jihadi propaganda with Guantanamo Bay and the first wave of prisoners who were held there at Camp X-Ray.

Fox News has learned that the video, which is being taken seriously by U.S. officials, is being analyzed by a group within the U.S. intelligence community that specializes in media exploitation. The Islamic State militant group, formerly known as the Islamic State of Iraq and Syria, is believed to have other Americans in their custody.

An intelligence source told Fox News that the landscape of the video is being analyzed to determine a likely location. Investigators also are planning to analyze the voices in the tape, including the masked executioner who appears to speak with a British accent, and whether or not the individual is linked to Britons known to have traveled to Syria.

British officials have said that several hundred people from Britain have traveled to Syria to join the battle against President Bashar Assad, and some may have crossed into Iraq as part of the rapid advance of the Islamic State group. French and German officials have recently put the combined total of those countries around 1,300.

Shiraz Maher of the International Center for the Study of Radicalization at King's College London, said the video was evidence that British jihadis were "some of the most vicious and vociferous fighters" in Syria and Iraq.

The masked militant in the clip speaks fluent English with what Lancaster University linguist Claire Hardaker said sounds like a London accent.

"Unfortunately the British participation in the conflicts now raging in both Syria and Iraq has been has been one of full participation, one that has seen them at the front lines, taking part in the conflict in every way," Maher told BBC radio. "So we have seen British fighters out there operating as suicide bombers, we have seen them operating as executioners."

The video prompted British Prime Minister David Cameron to return to London early from his vacation.

“He will meet with the foreign secretary and senior officials from the Home Office, Foreign Office and the agencies to discuss the situation in Iraq and Syria and the threat posed by [ISIS] terrorists," read a statement from the prime minister’s office.

Adam Schiff, D-Calif., who sits on House Intelligence Committee, called the video “appalling.”

"The apparent beheading of photojournalist James Wright Foley adds to the appalling parade of horrors perpetrated by [ISIS]. Seldom is the descriptor 'evil' applied with perfect accuracy as it is with this monstrous group that glories in death,” he said in a statement. “They know no human decency -- murdering journalists, beheading religious minorities refusing to convert, victimizing women and children, and starving entire communities.”

The release of the video comes amid a U.S. airstrike campaign against Islamic State targets in Iraq. ISIS has declared an Islamic state in the territory it controls in Iraq and neighboring Syria, imposing its harsh interpretation of Islamic law.

American fighter jets and drones conducted nearly a dozen airstrikes in Iraq since Tuesday, a U.S. official told The Associated Press.

According to the official, the latest airstrikes were in the area of the Mosul Dam and were aimed at helping Iraqi and Kurdish forces create a buffer zone at the key facility. The strikes, which now total nearly 90 since operations began, have helped Iraqi and Kurdish troops reclaim the dam from the insurgents.

Foley, 40, a freelance journalist, vanished in Syria in November 2012 while covering the Syrian civil war for GlobalPost. The car he was riding in was stopped by four militants in a contested battle zone that both Sunni rebel fighters and government forces were trying to control. He had not been heard from since.

The publication "mounted an extensive international investigation" for his whereabouts, with the search extending throughout the Middle East, along the Syria-Turkish border, in Lebanon, Jordan and other locations, GlobalPost reported Tuesday.

In 2011, Foley was among a small group of journalists held captive for six weeks by the government in Libya and was released after receiving a one-year suspended sentence on charges of illegally entering the country. In a May 2011 interview about his experience, he recounted watching a fellow journalist being killed in a firefight and said he would regret that day for the rest of his life. At the time, Foley said he would "would love to go back" to Libya to report on the conflict and spoke of his enduring commitment to the profession of journalism.

"Journalism is journalism," Foley said during the AP interview, which was held in GlobalPost's office in Boston. "If I had a choice to do Nashua (New Hampshire) zoning meetings or give up journalism, I'll do it. I love writing and reporting."

The New York-based Committee to Protect Journalists (CPJ) condemned what it called a "barbaric murder. The organization estimated Tuesday that about 20 journalists are missing in Syria, and has not released their nationalities.

In its annual report last November, CPJ concluded that the missing journalists are either being held and threatened with death by extremists, or taken captive by gangs seeking ransom. The group's report described the widespread seizure of journalists as unprecedented and largely unreported by news organizations in the hope that keeping the kidnappings out of public view may help in the captives' release.

Marquette University, Foley's alma mater, said it was "deeply saddened" by the news of Foley's death. The Milwaukee university said he had a heart for social justice and used his talents to tell stories in the hopes they might make a difference.

"We extend our heartfelt prayers and wishes for healing to James' family and friends during this very difficult time," Marquette University said in a statement.

Earlier Tuesday, GlobalPost CEO and co-founder Philip Balboni in a statement asked "for your prayers for Jim and his family." AFP chairman Emmanuel Hoog said the French news agency was "horrified" by the video and called Foley "a brave, independent and impartial journalist."

Click here for more from GlobalPost.

Fox News' Catherine Herridge and The Associated Press contributed to this report.