Peter Kassig, a 26-year-old aid worker who moved to Lebanon to bring aid to Syrian refugees in 2012, was confirmed dead on Sunday by the White House after ISIS released a video of his apparent execution.

Who Was Peter Kassig?

Kassig, an Indiana native, was a former U.S. Army Ranger who was deployed to Iraq in 2007. He was later honorably discharged for medical reasons and returned home, where he enrolled at Butler University to study political science. In 2012, after training as an EMT, getting married, and then getting quickly divorced, Kassig decided to go to Lebanon to learn more about the Syrian conflict during his spring break. In two weeks, Kassig said he “learned enough to know that I didn’t know anything,” and, after finishing up the semester, he took a leave of absence from school and relocated to Lebanon.

“We each get one life and that’s it. We get one shot at this and we don’t get any do-overs, and for me, it was time to put up or shut up. The way I saw it, I didn’t have a choice. This is what I was put here to do. I guess I am just a hopeless romantic, and I am an idealist, and I believe in hopeless causes,” Kassig told CNN in 2012.

His training as an EMT allowed him to begin volunteering at a hospital in Tripoli, Lebanon, through which he was further exposed to the harsh realities of war and life as refugees.

“War never ends, it just moves around… Loss and destruction in this land brings about only survival; the determination to press on and rebuild…because there is nothing else. To rubble and dust and back again. There’s just nothing else. I can’t be sure but I think I’m starting [to] believe that as beautiful as it is to finish building a house, it’s a better feeling laying the first brick again after it’s been torn down,” Kassig wrote in an e-mail to a friend in 2012.

Kassig then founded SERA International (Special Emergency Response and Assistance) in 2012 with the goal of becoming a relief organization that had the ability to work in conflict zones where bigger relief agencies may not be able to go. According to their website, SERA aimed to support medical training, deliver medical supplies and help any humanitarian efforts in refugee camps, hospitals and clinics in Lebanon and Syria. But, most importantly, Kassig hoped SERA would become an organization that works closely with those it aims to help.

“There are a lot of other wonderful organizations out there, but we feel that by working directly with the people who are in need at a grassroots level allows for us to establish an invaluable personal relationship that not only allows us to effectively distribute material goods but also allows for an opportunity for an increased level of cooperation and an exchange of ideas between people from diverse backgrounds and experiences and that this enhances our ability to accurately meet needs. The personal connection is key,” Kassig told Time in early 2013.

Kassig Converted To Islam While In Captivity

Kidnapped in October of 2013 while on his way to deliver medical supplies in Syria, Kassig lived in captivity for over a year before his death, during which time he converted to Islam and adopted the name Abdul-Rahman Kassig. In October 2014, a year after he was captured, Kassig appeared in the ISIS video of the execution of Alan Henning, a British aid worker. Following the public threat on Kassig’s life, Kassig’s parents, Ed and Paula Kassig, launched a campaign to try and save Kassig, filming a video message directly for ISIS.

According to those close to Kassig, and those who were held hostage along with him, Kassig voluntarily converted and relied heavily on his faith, so much so that his parents requested that their son be referred to as Abdul-Rahman in the press, and addressed him as such in a video plea released in October 2014.

During his capture, Kassig was able to send his parents a letter in which he spoke a bit about his faith and admitted he was “pretty scared to die.”

“I am obviously pretty scared to die but the hardest part is not knowing, wondering, hoping, and wondering if I should even hope at all. I am very sad that all this has happened and for what all of you back home are going through. If I do die, I figure that at least you and I can seek refuge and comfort in knowing that I went out as a result of trying to alleviate suffering and helping those in need,” Kassig wrote.

White House Confirms Peter Kassig’s Death

Following his death, Ed and Paula Kassig released a statement, writing, “We are incredibly proud of our son for living his life according to his humanitarian calling. We will work every day to keep his legacy alive as best we can.”

On Sunday, after ISIS released a video claiming to have killed Kassig, the White House confirmed Kassig’s death and released a statement: “While ISIL revels in the slaughter of innocents, including Muslims, and is bent only on sowing death and destruction, Abdul-Rahman was a humanitarian who worked to save the lives of Syrians injured and dispossessed by the Syrian conflict. While ISIL exploits the tragedy in Syria to advance their own selfish aims, Abdul-Rahman was so moved by the anguish and suffering of Syrian civilians that he traveled to Lebanon to work in a hospital treating refugees.”

Read the full statement below:

“Today we offer our prayers and condolences to the parents and family of Abdul-Rahman Kassig, also known to us as Peter. We cannot begin to imagine their anguish at this painful time.

“Abdul-Rahman was taken from us in an act of pure evil by a terrorist group that the world rightly associates with inhumanity. Like Jim Foley and Steven Sotloff before him, his life and deeds stand in stark contrast to everything that ISIL represents. While ISIL revels in the slaughter of innocents, including Muslims, and is bent only on sowing death and destruction, Abdul-Rahman was a humanitarian who worked to save the lives of Syrians injured and dispossessed by the Syrian conflict. While ISIL exploits the tragedy in Syria to advance their own selfish aims, Abdul-Rahman was so moved by the anguish and suffering of Syrian civilians that he traveled to Lebanon to work in a hospital treating refugees. Later, he established an aid group, SERA, to provide assistance to Syrian refugees and displaced persons in Lebanon and Syria. These were the selfless acts of an individual who cared deeply about the plight of the Syrian people.

“ISIL’s actions represent no faith, least of all the Muslim faith which Abdul-Rahman adopted as his own. Today we grief together, yet we also recall that the indomitable spirit of goodness and perseverance that burned so brightly in Abdul-Rahman Kassig, and which binds humanity together, ultimately is the light that will prevail over the darkness of ISIL.”