ISIS terrorist (illustrative)
ISIS terrorist (illustrative)Screenshot

The parents of Peter Kassig, the American aid worker who was beheaded by Islamic State (ISIS) terrorists, said Sunday night they were "heartbroken" by the death of their son.

"We are heartbroken to learn that our son, Abdul-Rahman Peter Kassig, has lost his life as a result of his love for the Syrian people and his desire to ease their suffering," Ed and Paula Kassig said in a statement posted on Twitter and quoted by AFP.

A video released earlier by ISIS showed the beheading of Kassig, who took the name Abdul-Rahman after converting to Islam, and that of 18 men described as Syrian military personnel.

His death was confirmed by President Barack Obama.

The 26-year-old was captured last year and was threatened in an October 3 video showing the beheading of British aid worker Alan Henning.

"Fed by a strong desire to use his life to save the lives of others, Abdul-Rahman was drawn to the camps that are filled with displaced families and to understaffed hospitals inside Syria," his parents wrote.

"We know he found his home amongst the Syrian people, and he hurt when they were hurting."

Kassig founded an aid group through which he trained some 150 civilians to provide medical aid to people in Syria. His group also gave food, cooking supplies, clothing and medicine to the needy.

"We are incredibly proud of our son for living his life according to his humanitarian calling," the Kassigs wrote, using the Twitter handle @kassigfamily.

"We remain eternally grateful for the many, many words of support and prayers from all over the world on our son's behalf."

Experts speculated earlier Sunday that Kassig may have struggled to the end with his captors.

This speculation is based mostly on the fact that the ISIS video claiming to show Kassig's decapitated head does not show Kassig making any statement to the camera prior to his execution. This is in stark contrast to previous videos in which orange jumpsuit-clad hostages are forced to issue statements against their governments before being beheaded.