Paris authorities said Monday that one of the Islamic State extremists involved in a video showing a beheaded U.S. aid worker and slaughtered Syrian soldiers is an Islamic convert Frenchman.

According to the Los Angeles Times, a French prosecutor, Francois Molins, said one of the militants pictured in the video released Sunday is 22-year-old Maxime Hauchard, who converted to Islam at age 17. The native of the Normandy region joined the extremists in Syria at the time of his conversion.

Molins said Hauchard left Paris on a flight to Istanbul, Turkey, with plans to cross into Syria, acting as if he was going to do humanitarian work.

French reports show that Hauchard gave an interview from Syria explaining how he had become radicalized through the Internet and that the goal of all Islamic State recruits is to assert martyrdom.

Hauchard is among the hundreds of French citizens who are believed to have traveled to Syria to join the Islamic State or other militants. Some of them converted to Islam while others are Muslim immigrants or the children of immigrants.

The Islamic State recruited over 1,000 Europeans while most of them entered Syria through Turkey. Turkish authorities have come under intense criticism for failing to track down the militants' travel across the border.

At least one other French citizen may be among the fighters pictured in the video.

U.S. officials confirmed that the video released by militants is real. The footage proves the execution of U.S. aid worker Peter Kassig, who was captured in Syria in October 2013 while on a private humanitarian mission. Kassig's cut-off head was seen at the foot of a militant but his actual beheading was not shown.

The 26-year-old former U.S. soldier served in the Iraq conflict and founded an aid organization to help Syrians. He is the fifth Westerner known to have been beheaded by Islamic State forces following the executions of U.S. journalists James Foley and Steven Sotloff, and two British aid workers.