ISIS Terror

Friend of Peter Kassig: Beheaded Humanitarian ‘Didn’t Give In’ to Fear

Friend of ISIS Victim: 'Pete Was the Nicest Guy' 0:38

Murdered U.S. aid worker Abdul-Rahman Kassig was an "incredible guy" with a "big heart," his former roommate told NBC News.

The militant group ISIS announced the death of Kassig, 26, in a grisly propaganda video released on Sunday. Kassig — who went by the name Peter before he converted to Islam — was captured in Syria in October 2013 and ISIS had warned he would be executed. Friends, family and colleagues had issued public appeals for mercy.

"You think you are prepared for it but nothing can really prepare you for this," his friend Michael Downey told NBC News in an interview after Kassig's death was confirmed. "The most important thing is remembering the person for who he was and the incredible work that he did and everything that he gave to help people."

Downey said he'd first met Kassig in Beirut in 2012 when the young man from Indiana came to stay in his apartment. Kassig — who Downey said greeted everyone with a smile, hug and the endearing term "brother" — stayed on his couch for almost a month.

"He had this unrelenting positivity and it was infectious," Downey said. While some people who'd been exposed to so much horror in his work could become cynical or jaded, Kassig "never had room" for that, Downey explained.

"There's very few individuals you meet that are so selfless and that truly want to help people and that put everyone else before them," Downey said. "If there are more people like him the world would be a much better place."

Downey said the last time he had spoken to Kassig was on Skype on Sept. 27, when his former roommate mentioned he was going on another run to bring into Syria.

"He said 'alright, we'll talk soon, I'll be out in a few days,'" Downey said. "Then I never heard back from him."

Downey said that Kassig was aware of the risks — kidnapping, death — which faced him in Syria, but felt compelled to go there and bring medical supplies.

"The main message of this," Downey said, fighting back his emotions, is that Kassig didn't "give into the fear and intimidation that ISIS really thrive off of."

"That's something we can all learn from," he added.

— Sarah Burke