The families of four American hostages who were killed while in Islamic State custody issued a joint letter Wednesday imploring the Obama administration to “use all appropriate means” to find and return missing U.S. journalist Austin Tice. 
 
 Tice is the last unaccounted-for American reporter in the Syrian civil war; he was abducted by unknown gunmen in August 2012 and has been incommunicado ever since. Tice’s parents have asked the White House to step up search efforts, with their calls sounding increasingly urgent as the clock runs out on the Obama administration’s final term. 
 
 State Department spokesman John Kirby said U.S. officials are working through the Czech government, the U.S. protecting power because the U.S. embassy in Damascus is shuttered, to find information on Tice’s “welfare and whereabouts.” Kirby said officials are in regular contact with families of U.S. detainees overseas, but that privacy considerations prevented him from saying more about Tice. 
 
 “We are deeply concerned about the well-being of Austin Tice,” Kirby said. “His case has the attention of the highest levels in the U.S. government and the administration.” 
 
 The letter the Tices released Wednesday bore the names of the slain hostages’ parents – a raw reminder of search efforts that didn’t find captives in time. They represented journalists James Foley and Steven Sotloff, and humanitarian aid workers Abdul-Rahman Peter Kassig and Kayla Mueller. 
 
 The Islamic State beheaded Foley, Sotloff and Kassig in gruesome propaganda videos. Mueller, who reportedly was enslaved and assaulted for months by Islamic State leader Abu Bakr al Baghdadi, died in a coalition strike, apparently an inadvertent casualty of the U.S.-led campaign targeting the Islamic State’s so-called caliphate in Iraq and Syria. 
 
 We are four families bonded together by tragedy and terror. . . . But there is something that still can be done: Bring Austin Tice safely home. Open letter to President Obama 
 
 The Tices got to know the other families when they united to lobby for changes in hostage policy – they were at the White House together a year ago this week when President Barack Obama announced a revamped process based on the families’ recommendations. 
 
 “We are four families bonded together by tragedy and terror. We will never fully recover from the horrific outcome of our own hostage crisis,” the families of the slain captives wrote in the joint letter. “But there is something that still can be done: Bring Austin Tice safely home.” 
 
 Neither the Tices nor the other families named specific steps the Obama administration could take to find Tice and win his release. They alluded to diplomatic efforts and urged officials not “to hesitate in leveraging all appropriate means.” The parents also chided Obama for failing to mention Tice – the only U.S. journalist in captivity in the world – during his high-profile speech at the annual White House Correspondents Association dinner April 30. 
 
 Austin Tice is the only American journalist being held captive in the world. 
 
 “We are not asking the White House to put anyone in harm’s way, nor compromise national security,” the families wrote. “We are asking the president, fully within the responsibilities and obligations of his office, to put aside any personal or election year concern, to engage boldly and to use all appropriate means to bring Austin Tice safely home as soon as possible.” 
 
 The families gave wrenching testimonials about having a loved one held hostage in Syria. 
 
 Mueller’s parents and brother, Carl, Marsha and Eric, wrote that they are “haunted every day” and urged the government not to repeat what they deemed as missed opportunities and “the deadly silence that cost all the hostages their lives.” 
 
 Foley’s parents, Diane and John, told Obama that they’re counting on him to keep the promises he made “after the horrific execution of our son.” Kassig’s parents, Ed and Paula, said they’re “devastated by the loss of our son, but the pain will be slightly lessened” if his death spurred the government to act urgently to bring Tice home. 
 
 Shirley and Arthur Sotloff were even more direct. 
 
 “We, the family of the late journalist Steven Sotloff, remind President Obama of the following: You told us in person that if it were your daughters, you would do anything in your power to bring them home,” they wrote. “We implore you: Bring Austin Tice home.” 
 
 EDITORS: STORY CAN END HERE 
 
 Tice, now 34, a U.S. Marine-turned-journalist who reported for outlets including McClatchy and The Washington Post, vanished in Syria in mid-August 2012. Apart from a video clip showing him in the custody of unknown gunmen shortly after his disappearance, there’s been no confirmed sighting of Tice since. 
 
 Unlike the other American captives, Tice is widely believed to have been seized by loyalists of the Syrian regime – not by the Islamic State. Damascus denies any knowledge of his whereabouts. This August will mark his fourth year in apparent detention. 
 
 The parents of the hostages closed their letter of support by recognizing the Tice family’s anguish. They, too, know how “it requires mountain-moving faith to maintain hope as the crisis continues.” 
 
 “With unwavering hope, Austin’s parents do not give up,” the families wrote. “The United States government must not give up.” ||||| An attempt to rescue Kayla Mueller and other American hostages occurred in a July 4 raid previously disclosed by the Pentagon. 
 
 U.S. special forces commandos conducted a raid in the predawn hours on a prison in Islamic State's Syrian stronghold of Raqqah. 
 
 But the mission was unsuccessful because hostages -- which included Mueller as well as American journalists James Foley and Steven Sotloff -- had already been moved and weren't there at the time. 
 
 "We never stopped trying to get her," said a defense official, who wasn't authorized to speak publicly on the matter. "We never lost that focus." 
 
 President Obama confirmed for the first time Tuesday that Mueller was one of the hostages Delta Force commandos ‎attempted to rescue in a raid on an oil refinery facility in northern Syria in summer 2014. The two dozen commandos arrived a day or two after the hostages had been moved from the site, Obama said. 
 
 "I deployed an entire operation -- at significant risk -- to rescue not only her but the other individuals who had been held, and probably missed them by a day or two," Obama said during an interview with BuzzFeed News. 
 
 Obama said the U.S. has a commitment to devote "enormous" resources to free hostages anywhere in the world.‎ 
 
 Relatives of Mueller, who was abducted while volunteering in Syria, announced Tuesday that they had received confirmation that she is dead. 
 
 CAPTION Friends, family praise Kayla for her empathy, compassion Friends, family praise Kayla for her empathy, compassion CAPTION Friends, family praise Kayla for her empathy, compassion Friends, family praise Kayla for her empathy, compassion CAPTION The family of hostage American aid worker Kayla Mueller says they have received confirmation of her death. The family of hostage American aid worker Kayla Mueller says they have received confirmation of her death. CAPTION White House confirms death of hostage Kayla Mueller White House confirms death of hostage Kayla Mueller 
 
 Islamic State released a video last week claiming that Mueller, 26, was killed in an air attack by coalition forces against the militants in Syria. 
 
 U.S. intelligence officials believe that Mueller is dead but don't accept the militants' account of how she was killed, White House Press Secretary Josh Earnest said in Washington on Tuesday. 
 
 There was no evidence civilians were in the area that was targeted by Jordan on Friday, Earnest said. 
 
 The Pentagon confirmed that Jordanian warplanes bombed a weapons storage facility Friday, but there was no indication that Mueller was there at the time, said Rear Adm. John Kirby, a Pentagon spokesman. 
 
 “We do not know the circumstances surrounding her death,” he said. “U.S. intelligence had no evidence that there were any civilians at the location of this weapons storage facility that was struck by Jordanian F-16s.” 
 
 The building, a facility near the Islamic State stronghold of Raqqah, was hit Friday and at least twice before, he said. 
 
 Regardless of how Mueller died, he said, her Islamic State captors were to blame. “They are responsible for her safety and well-being,” Earnest said. 
 
 Mueller's family members released a statement saying that they had received confirmation of her death. They did not disclose how they learned the information. 
 
 However, a source close to the family who requested anonymity because of the sensitive nature of the communications said a private message containing additional information from the captors was sent to Mueller's parents over the weekend. Once the statement was authenticated by the intelligence community, the family concluded that she was dead, the source said. 
 
 “We are heartbroken to share that we’ve received confirmation that Kayla Jean Mueller has lost her life,” her parents, Carl and Marsha Mueller, and her brother, Eric, said in the statement. 
 
 U.S. officials are aware of at least one other American being held in the region, Earnest said. He did not identify the individual, or the group holding the captive. But he may have been referring to Austin Tice, an American journalist and former Marine who disappeared in Syria in August 2012. 
 
 It is unclear who is holding Tice, but his parents, Debra and Marc Tice, have said that they don't believe he is in the hands of Islamic State militants. 
 
 "Our hearts go out to the Mueller family and everyone who loves Kayla," the family said in a statement posted on a website that aims to raise awareness about Austin Tice's captivity. "We have no way of understanding what they are going through, and we wish them all possible comfort." 
 
 In Washington, the White House released a statement of condolence from President Obama. 
 
 "On behalf of the American people, Michelle and I convey our deepest condolences to Kayla’s family -- her parents, Marsha and Carl, and her brother Eric and his family -- and all of those who loved Kayla dearly," the statement said. "At this time of unimaginable suffering, the country shares in their grief." 
 
 Mueller had a long history of volunteering to help women and children, having worked for aid groups in Arizona before setting out for other countries, including India and Turkey. 
 
 In August 2013, she was abducted in the Syrian city of Aleppo as she left a hospital operated by Doctors Without Borders and was being held in Raqqah, a militant stronghold in northeastern Syria. 
 
 The family statement also included letters Mueller wrote to her family, including one on her father’s birthday in 2011. 
 
 “Some people find God in church. Some people find God in nature. Some people find God in love,” she wrote. “I find God in suffering. I’ve known for some time what my life’s work is, using my hands as tools to relieve suffering.” 
 
 After attending Northern Arizona University, she worked with aid groups in northern India, Israel and the Palestinian territories. She returned to Arizona in 2011, where she worked at an HIV/AIDS clinic and volunteered at a women's shelter. Late that year, she moved to southeastern France and worked as an au pair while learning French in preparation for a planned move to Africa. 
 
 But the plight of families fleeing the violence in war-torn Syria drew her to Turkey in December 2012. She worked with the aid groups Support to Life and the Danish Refugee Council, assisting women and children who crossed into Turkey as refugees. 
 
 She also made some trips into Syria to help reconnect family members separated by the fighting. Her trips into the country took her to Aleppo, where she was eventually kidnapped. 
 
 In correspondence to her family, which she slipped to other detainees who were being freed, Mueller was contrite and seemed to try to assuage her family’s worry. She told them she was being treated well and was not in harm’s way. 
 
 “If you could say I have ‘suffered’ at all throughout this whole experience it is only in knowing how much suffering I have put you all through; I will never ask you to forgive me as I do not deserve forgiveness,” Mueller wrote in a letter the family said it received in the spring of last year. 
 
 She said in the letter that she was willing to wait for her freedom if it meant that her family would be absolved of the burden of negotiating her freedom. ||||| WASHINGTON -- Kayla Jean Mueller, a 26-year-old American woman held by Islamic State of Iraq and Syria (ISIS) militants, has been confirmed dead, her parents and the Obama administration said Tuesday. 
 
 CBS News national security correspondent David Martin reports that ISIS sent the family an e-mail telling them their daughter was dead and including a picture. The picture showed that she had died "recently" but the cause and exact date of her death were inconclusive. The U.S. intelligence community was then able to verify the photo. 
 
 "We are heartbroken to share that we've received confirmation that Kayla Jean Mueller, has lost her life," Carl and Marsha Mueller said in a statement. "Kayla was a compassionate and devoted humanitarian. She dedicated the whole of her young life to helping those in need of freedom, justice, and peace." 
 
 President Barack Obama said that Mueller, who was an aid worker who assisted humanitarian organizations working with Syrian refugees, "epitomized all that is good in our world." 
 
 "No matter how long it takes, the United States will find and bring to justice the terrorists who are responsible for Kayla's captivity and death," the president said. 
 
 The White House said Obama had spoken with Mueller's parents and offered his condolences and prayers. 
 
 Mueller, of Prescott, Arizona, is the fourth American to die while being held by ISIS militants. Three other Americans - journalists James Foley and Steven Sotloff, and aid worker Peter Kassig - were beheaded by the group. 
 
 Journalist Austin Tice, of Houston, Texas, disappeared in August 2012 while covering Syria's civil war. It's not clear what entity is holding him, but it is not believed to be ISIS or the Syrian government, his family has said. 
 
 Mueller was taken into captivity in August 2013 while leaving a hospital in Syria. Her identity was long kept secret out of fears for her safety. 
 
 On Friday, ISIS claimed that Mueller died in a Jordanian airstrike. Jordan, which has launched a barrage of strikes in recent days in retaliation for the gruesome killing of one of its pilots at the hands of the militants, disputed that report. 
 
 In the U.S., there was growing certainty that the claim from ISIS was false. White House spokesman Josh Earnest said that Jordan's airstrikes had targeted an ISIS weapons compound near the group's stronghold of Raqqa in northern Syria that had been targeted before, and that there was no evidence that civilians were in the area ahead of the strike. 
 
 Navy Rear Adm. John Kirby was asked Tuesday if there was any doubt who killed the aid worker. He replied: "No doubt. ISIL," using another acronym the group is known by. 
 
 Mueller had been working in Turkey assisting Syrian refugees, according to a 2013 article in The Daily Courier, her hometown newspaper. She told the paper that she was drawn to help with the situation in Syria. 
 
 "For as long as I live, I will not let this suffering be normal," she said. "It's important to stop and realize what we have, why we have it and how privileged we are. And from that place, start caring and get a lot done." 
 
 According to the newspaper, Mueller had been working with the humanitarian aid agency Support to Life, as well as a local organization that helped female Syrian refugees develop skills. 
 
 Secretary of State John Kerry said the U.S. was "unshaken" in its resolve to defeat the Islamic State, a group he called an "ugly insult to the civilized world." 
 
 Republican Sen. John McCain, who represents Mueller's home state of Arizona, said, "The thoughts and prayers of the people of Arizona, America, and the civilized world are with the Mueller family at this terrible hour." 
 
 Mueller's father briefly had a glimmer of hope that his daughter might be rescued but was mostly overwhelmed by "devastation and hopelessness" during the year and a half that his daughter was held captive by ISIS, a family friend told CBSN on Tuesday. 
 
 Mueller's family said she graduated from Northern Arizona University in 2011 after just two-and-a-half years. In December 2012, she traveled to the Turkish-Syrian border to work with several humanitarian groups, including Support to Life and the Danish Refugee Council. 
 
 Mueller's family said, "We are so proud of the person Kayla was and the work that she did while she was here with us. She lived with purpose, and we will work every day to honor her legacy." 
 
 Mueller's parents released a letter Tuesday that their daughter had written them while in captivity. In the undated letter, Mueller said she was, "in a safe location, completely unharmed." 
 
 "I am also fighting from my side in the ways I am able + I have a lot of fight left inside of me," she wrote. "I am not breaking down + I will not give in no matter how long it takes."
– American journalist Austin Tice—believed to be the only US reporter held hostage anywhere in the world—was captured in Syria in August 2012. Since then, US hostages James Foley, Peter Kassig, Kayla Mueller, and Steven Sotloff have been killed, and their families fear Tice's parents will soon have to share in their heartbreak. "We are four families bonded together by tragedy and terror," they write in an open letter to Obama at McClatchy. "But there is something that still can be done: Bring Austin Tice safely home." The letter comes a year after Obama promised the US would improve on how it dealt with hostages. "You told us in person that if it were your daughters, you would do anything in your power to bring them home," says the letter. "We are not asking the White House to put anyone in harm's way, nor compromise national security," but to "engage boldly and use all appropriate means to bring Austin Tice safely home as soon as possible." The editorial board of the Sacramento Bee is backing the families. "The US military has a solemn creed: No soldier left behind," it writes. "The same should hold true for Austin Tice." A State Department rep tells McClatchy that Tice's case "has the attention of the highest levels in the US government and the administration."