Story highlights French citizen believed to appear in ISIS video was "self-radicalized," prosecutor says

Maxime Hauchard traveled to Syria in 2013, Interior Minister Bernard Cazeneuve says

Hauchard's involvement only alleged but "high probability" it was him, Cazeneuve says

The video in which he's said to appear widely considered ISIS' most brutal to date

France's interior minister said Monday that based on intelligence analysis, "a strong presumption exists" that a French citizen named Maxime Hauchard participated in the "despicable crimes" shown on the latest video from ISIS.

The video released over the weekend depicts the slayings of several men described by ISIS as Syrian soldiers and appears to show the aftermath of the beheading of U.S. aid worker Peter Kassig.

While Hauchard's involvement is only alleged and investigations continue, Interior Minister Bernard Cazeneuve said intelligence analysis of the video suggests "a very high probability that a French citizen has directly participated in the execution of these despicable crimes."

Public Prosecutor Francois Molins said authorities are investigating the possibility that a second French citizen may have been involved in the killings shown on the video.

Hauchard, 22, went to Syria in 2013 after visiting Mauritania the previous year, Cazeneuve said.

According to Molins, Hauchard is a "self-radicalized" jihadist who traveled to Syria under the guise of a humanitarian mission. He was known to French security services as far back as 2011, the prosecutor said.

In July, Hauchard spoke to French broadcaster BFM, describing life as a fighter.

An image grab, taken from a propaganda video released on November 16, 2014, allegedly shows an ISIS member believed to be French citizen Maxime Hauchard.

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"Everything is paid for. Clothes are paid for. Weapons are not ours, we don't pay for them. Same for the missions, the guns," he said, according to a CNN translation of his remarks. "The other day I wanted to buy shampoo. I wrote it down on the list -- we have a list where we write down stuff. Then the boss goes out shopping at the market. And he brings us back the shampoo, for example, without making us pay."

"The goal as a group, the goal as a community is to establish the laws of Allah on Earth," he said. "But from a personal point of view, it is martyrdom."

The video in which Hauchard is said to have appeared is widely considered the most brutal yet released by the terror group, which is also known by the acroynm ISIL as well as its self-given name, the Islamic State.

U.S. President Barack Obama, in confirming Kassig's beheading, called the executions "pure evil by a terrorist group that the world rightly associates with inhumanity."

The 16-minute production includes a lengthy segment on the group's history and shows in graphic detail beheadings of several men described as Syrian military pilots.

Several men without masks, presumably ISIS fighters, are shown in that segment killing the men.

The video doesn't show Kassig's death but does show a masked man dressed in black, speaking in what sounds like a English accent. A similar figure appeared in earlier videos depicting the apparent beheadings of Westerners.

Kassig is the fifth Western hostage to be killed by ISIS since the United States and its allies began airstrikes against ISIS in August.

ISIS is believed to be holding at least two more Western hostages: a 26-year-old female, American aid worker, and John Cantlie, a British journalist, who has appeared in a number of ISIS-produced videos.

U.S. officials have credited the air campaign with stopping a wildly successful ISIS ground offensive and disrupting the group's ability to finance and plan its exploits.

On Monday, the U.S. military said coalition warplanes conducted 31 airstrikes against ISIS targets in Syria and Iraq between Friday and Monday, hitting fighting positions, staging areas and units in the field, among other targets.