Peter Kassig

The state prosecutor said that Mickael Dos Santos was a 22-year-old man from a town east of Paris who converted to Islam and left for Syria in August 2013

Hundreds of young men from Western countries are said to have left their families behind to fight for Islamic State

Twenty-six-year-old Kassig was taken captive on his way to the eastern Syrian city of Deir al-Zor on Oct. 1, 2013

The 26-year-old Indianapolis native was first captured on October 1, 2013 while delivering hospital supplies in Deir Ezzour, Syria.

The Islamic State has threatened to next kill American aid worker Abdul-Rahman Kassig, who was working for a medical aid organization when he was taken hostage in October 2013

Peter Kassig, currently being held hostage by ISIS, was captured while working as an aid worker