Once a happy-go-lucky student at one of Brussels' most prestigious high schools, Abdelhamid Abaaoud has turned into Belgium's most notorious jihadi - so devoted to the cause that he recruited his 13-year-old brother to join him in Syria.
Abaaoud is the child of Moroccan immigrants who grew up in the Belgian capital's scruffy and multi-ethnic Molenbeek-Saint-Jean neighbourhood.
The fugitive, who is in his late 20s, was identified by French authorities on Monday as the presumed mastermind of the attacks in Paris that killed 129 people and injured hundreds.
Abaaoud is also believed to have links to earlier terror attacks that were thwarted: one against a Paris-bound high-speed train that was foiled by three young Americans in August, and the other against a church in the French capital's suburbs, according to officials.
"All my life, I have seen the blood of Muslims flow," Abaaoud said in a video made public in 2014. "I pray that Allah will break the backs of those who oppose him, his soldiers and his admirers, and that he will exterminate them."
Belgian authorities suspect him of also helping organise and finance a terror cell in the eastern city of Verviers that was broken up in an armed police raid on January 15, in which two of his presumed accomplices were killed.
The following month, Abaaoud was quoted by Islamic State's English-language magazine Dabiq as saying that he had secretly returned to Belgium to lead the terror cell and then escaped to Syria in the aftermath of the raid, despite having his picture broadcast across the news.
He boasted: "I was even stopped by an officer who contemplated me so as to compare me to the picture, but he let me go, as he did not see the resemblance!"