Peter Kassig is shown with a truck loaded with supplies. The Islamic State group released a video Sunday in which a black-clad militant claimed to have beheaded Kassig, who was providing medical aid to Syrians.

BEIRUT — A young Frenchman is believed to be among the killers on an Islamic State propaganda video showing a beheaded American aid worker and the deaths of more than a dozen Syrian soldiers, France's top security official said today.

Interior Minister Bernard Cazeneuve said there is a “strong presumption” that Maxime Hauchard is among the group of Islamic extremist fighters in the video released over the weekend. He urged young people in France to “open your eyes to the terrible reality” of the militant group.

Cazeneuve said authorities were analyzing the video and have been investigating Hauchard, who is around 22 years old and from west of Paris. The convert to Islam gave an interview to France's BFM television in July, telling the network he had helped in the capture of Mosul, the Iraqi city whose fall eventually prompted the United States to resume military operations there.

French citizens make up the largest contingent of European jihadi fighters who have joined extremists in Syria and Iraq. According to the Paris prosecutor's office, about 1,100 people have been placed under surveillance, and 95 people face charges.

Hauchard, who is believed to have arrived in Syria in 2013, is among those under judicial investigation, Cazeneuve said.

The Islamic State group beheaded Peter Kassig, releasing a video Sunday showing a masked militant standing over the severed head of a man it said was the former U.S. Army Ranger-turned-aid worker, who was seized while delivering relief supplies in Syria last year.

President Barack Obama confirmed Kassig's slaying after a U.S. review of the video, which also showed the mass beheadings of a dozen Syrian soldiers.

The 26-year-old Kassig, who founded an aid group to help Syrians caught in their country's brutal civil war, “was taken from us in an act of pure evil by a terrorist group that the world rightly associates with inhumanity,” Obama said.

He denounced the extremist group, which he said “revels in the slaughter of innocents, including Muslims, and is bent only on sowing death and destruction.”

The slain hostage's parents, Ed and Paula Kassig, said they were “heartbroken” by their son's killing, but “incredibly proud” of his humanitarian work.

With Kassig's death, the Islamic State group has killed five Westerners it was holding. American journalists James Foley and Steven Sotloff were beheaded, as were British aid workers David Haines and Alan Henning.

Unlike previous videos of slain Western hostages, the footage released Sunday did not show the decapitation of Kassig or the moments leading up to his death.

The high-definition video also showed the beheadings of about a dozen men identified as Syrian military officers and pilots.