FLAGSTAFF, Ariz. (AP) -- The parents of slain hostage Kayla Mueller say they once asked their daughter to stop doing humanitarian work in Syria but she insisted the struggle of refugees was her struggle too.
Carl and Marsha Mueller say Kayla was the most fulfilled when she was helping to ease suffering in the world, the Arizona Daily Sun reported.
"It was hard not to let Kayla go to all these places she did because it gave her so much joy," Marsha Mueller said.
"The more she helped, the more she got."
Marsha Mueller, Kayla's mother
The Muellers made their remarks Friday night during an event honoring their daughter at her alma mater, Northern Arizona University.
Carl said he remembered asking his daughter to come home.
"I was angry. I said, 'This is not your war, these are not your people. You don't need to die for this. Come home," he said, then read aloud the words she wrote back.
"I do believe this is my struggle," Kayla wrote. "Really, in the end, the real reason that 100,000 lives have been lost in Syria is not because people don't care, or don't have sympathy or compassion. But rather it's because people are under the illusion that this is not their struggle, it is not their people and it's not their concern."
The Prescott couple says since her death, they have had moments of gratitude hearing from people all over the world who Mueller befriended.
"Kayla was like a voice in the deep forest screaming the truth and screaming reality but nobody was there to listen, nobody could hear," Carl said. "But now she's being heard, she's affecting people all over the world."
Mueller, whose death was confirmed in February by U.S. officials, was taken hostage by the Islamic State group in August 2013 after leaving a hospital in Aleppo, Syria.
For more on Kayla Mueller, scroll through the gallery below:
Kayla Jean Mueller -- ISIS Hostage, Kayla Mueller
Slain aid worker's parents share memories at university
Courtesy: Mueller Family
#Obama confirms death of American #ISIS #hostage Kayla Mueller; Private Message from ISIS sent to Parents of ISIS Hostage, Kayla Mueller, Confirms Her Death http://read.bi/16QUgjt
Statement from the White House on the death of Kayla Mueller
Parents of #ISIS hostage Kayla Mueller urge her captors to contact them. http://t.co/oYOzFBF62r http://t.co/DTkx9od38u
The Mueller family have released new pictures of Kayla. http://t.co/vk7warF4OQ
The parents of American Islamic State (ISIS) hostage Kayla Mueller, who the extremist group claims was killed Friday by a Jordanian airstrike on the Syrian city of Raqqa, are hopeful that their daughter is still alive. Carl and Marsha Mueller said in a statement on Friday, "This news leaves us concerned, yet, we are still hopeful that Kayla is alive." Mueller's parents urged ISIS to contact them privately, and to treat their daughter as a guest.
.@ejmontini: For Kayla Mueller's family, waiting is not a game http://t.co/TvtOCrgFJv http://t.co/GEaSQNdKKv
Prescott stricken by loss, uncertainty of Kayla Mueller's fate. via @RebekahLSanders
Family, others kept Kayla Mueller's capture a secret to protect her, @KarenBrown3TV reports http://t.co/bHlvjWYAqw http://t.co/noUUfRUS6m
Family of hostage Kayla Mueller breaks silence after #IslamicState claims: http://t.co/Dv5w7uOFwW | http://t.co/iSNja0KShX
JUST IN: ISIS sent Muellers an e-mail saying their daughter was dead and included a photo, David Martin reports; cause of death inconclusive
A local Palestinian man holds up a poster of slain ISIS hostage Kayla Mueller who worked in Palestine and was an activist with the International Solidarity Movement- a movement dedicated to supporting a free Palestinian state. In the Palestinian West Bank village of Bilin, west of Ramallah, the 10th anniversary of the popular resistance movement against the Israeli occupation was held on Friday afternoon. Israeli soldiers invaded the village on Friday, stopping protesters from marching into the olive orchards. Israeli soldiers assaulted Palestinians and international activists, beating them, spraying them with a chemical orange agent, as well as using hundreds of tear gas canisters. Live ammunition rounds were also fired at protesters, including sound bombs thrown at the feet of journalists. Journalists who were filming the protests were assaulted by Israeli soldiers as well. The village gained global notoriety when a decade ago locals as well as international activists would gather and organize weekly protests on Fridays, marching towards olive orchards and lands that were confiscated by the Israeli government to build illegal settlements and the separation barrier in the West Bank. The village gained even more popularity after one of its locals, Emad Burnat, filmed the Oscar-nominated film, Five Broken Cameras in which he showed the struggle of the Palestinian village against Israeli aggression. Scores of people, both Palestinian and international have been injured during weekly protests, the most infamous of whom was Basem Au Rahma who was killed in 2009 when a tear gas canister struck him in the chest. Two years later, in 2011, Jawaher Abu Rahma also died during a weekly protest after being hit with a tear gas canister. (Photo by Anna Ferensowicz/Pacific Press/LightRocket via Getty Images)
Palestinian protesters hold placard to protest against 'terrorism' on February 13, 2015 before a demonstration against Jewish settlements in the West Bank village of Bilin, west of Ramallah. The poster shows a picture of US aid worker Kayla Mueller, who died as a hostage of Islamic State (IS) group jihadists. (Photo credit ABBAS MOMANI/AFP/Getty Images)
Palestinian protesters hold placard to protest against 'terrorism' on February 13, 2015 before a demonstration against Jewish settlements in the West Bank village of Bilin, west of Ramallah. The posters show pictures of US aid worker Kayla Mueller, who died as a hostage of Islamic State (IS) group jihadists. (Photo credit ABBAS MOMANI/AFP/Getty Images)