An American held captive for two years by an al-Qaeda-linked group in Syria was released Sunday, according to the Obama administration and his family.
"For two years, we have kept Peter Theo Curtis, a U.S. citizen held hostage in Syria, in our thoughts and prayers," White House national security adviser Susan Rice said in a statement. "Today, we join his family and loved ones in welcoming his freedom."
Curtis, 45, who is from Massachusetts, was held by the Jabhat al-Nusra, also known as the al-Nusra Front, a branch of al-Qaeda operating in Syria, Secretary of State John Kerry said in a statement.
Curtis is a published author and freelance journalist who writes under the name Theo Padnos, according to a statement released Sunday by his family expressing gratitude to the United States, Qatar and others who helped negotiate his release. He was captured shortly after he crossed into Syria in October 2012.
"My heart is full at the extraordinary, dedicated, incredible people, too many to name individually, who have become my friends and have tirelessly helped us over these many months," his mother, Nancy Curtis from Cambridge, Mass., said in the statement. "Please know that we will be eternally grateful."
Nancy Curtis said the family did not know the details surrounding the negotiation for Curtis' release but said they "were repeatedly told by representatives of the Qatari government that they were mediating for Theo's release on a humanitarian basis without the payment of money."
Qatar's Foreign Ministry confirmed late Sunday that the Gulf emirate succeeded in gaining Curtis' release. "(Qatar) exerted relentless efforts to release the American journalist out of Qatar's belief in the principles of humanity and out of concern for the lives of individuals and their right to freedom and dignity," according to a government statement released by the Qatar News Agency.
Curtis was handed over to United Nations peacekeepers in Golan Heights on Sunday evening, according to a U.N. statement. After receiving medical attention, he was handed over to U.S. government representatives, the statement said.
"Over these last two years, the United States reached out to more than two dozen countries, asking for urgent help from anyone who might have tools, influence or leverage to help secure Theo's release and the release of any Americans held hostage in Syria," Kerry said.
President Obama, who was wrapping up a vacation in Massachusetts, was briefed Sunday morning on Curtis' release.
"The president shares in the joy and relief that we all feel now that Theo is out of Syria and safe," White House spokesman Eric Schultz said. "But we continue to hold in our thoughts and prayers the Americans who remain in captivity in Syria, and we will continue to use all of the tools at our disposal to see that the remaining American hostages are freed."
Footage of Curtis, in a video obtained by Al-Jazeera and The New York Times in late June, showed the American looking disheveled. Speaking from a script, Curtis stated his name and said he was a journalist from Boston, Al-Jazeera reported. He said his captors treated him well, and he "had everything" he needed, the Times reported.
In a video obtained by the Associated Press dated July 18, Curtis appears to read from a sheet and pleads for the U.S. and European governments to contact a named intermediary.
"They have given me three days to live," he says as a man holding an assault rifle and dressed in camouflage stands next to him. "If you don't do anything, I'm finished. I'm dead. They will kill me. Three days. You have had 20 days, and you've done nothing. "
Curtis, under the Theo Padnos byline, has written for the New Republic and in 2011 wrote a book called Undercover Muslim: A Journey Into Yemen, which studied the radicalization of disaffected youths.
"He seems to be in good health," Curtis' cousin Viva Hardigg told the Associated Press on Sunday. "We are deeply relieved and grateful for his return and the many people who have helped us secure his freedom. At the same time, we are thinking constantly of the other hostages who are still held and those working to help them be freed. We want to do everything we can to support their efforts."
Rice said Curtis will be reunited with his family shortly. His release comes days after the Islamic State released a video showing the beheading of James Foley, 40, an American freelance reporter.
"We will continue to work tirelessly on behalf of all Americans who are held overseas so that they can be reunited with their families as well," Rice said.
Steven Joel Sotloff, a photojournalist and former University of Central Florida student, remains a hostage of the terrorist group and was threatened with death in the same video that portrayed Foley's killing.
Nancy Curtis said in a statement that she had gotten to know the Foley family and appealed to the captors of remaining hostages to release them.
"My entire focus right now is on helping the other families of those still being held in Syria and on taking care of my son," she said.
Contributing: The Associated Press