In the words of Koen Geens, the Belgian justice minister, he changed from a student at an upscale Brussels school into “an extremely professional commando”, one seemingly able to slip across borders at will.
Someone who openly mocked the inability of Western law enforcement agencies to catch him.
On Wednesday, the son of an immigrant shopkeeper from Morocco fought his last battle. Police raided a suburban Paris apartment where he was hiding.
The wanted jihadi’s own father believes prison, where he served time for petty crimes, changed him for the worse.
After his son got out, Omar Abaaoud noticed “signs of radicalisation”, the elder Abaaoud’s lawyer, Nathalie Gallant, told RTBF broadcasting.
If so, that would fit the pattern of a number of jihadis who were radicalised in prison.
A person in Belgium familiar with the investigation told the Associated Press that Abaaoud became “close”, while living in the Molenbeek neighbourhood, to another immigrant’s son, Brahim Abdeslam.
On Friday, Abdeslam was one of the suicide bombers who blew himself up in the murderous wave that shook Paris.
Abdeslam’s brother Salah, who authorities say was also an acquaintance of Abaaoud, is being sought as a suspected accomplice.
Abaaoud came on to the international radar as a radical Muslim combatant for the first time in February 2014, said Jasmine Opperman, a senior director with the independent Terrorism Research & Analysis Consortium (TRAC).
Western recruits had flocked to Syria from Europe and elsewhere to battle the forces of Syrian president Bashar Assad, and fighters from Belgium and other French-speaking countries were co-ordinating assaults north of Aleppo.
During the campaign, Abaaoud was filmed at the wheel of a pickup truck dragging a load of mutilated bodies following a mass execution committed by Islamic State at a place called Hraytan.
“His father was very much against him going there,” the Belgian source told AP. But there was much worse news for the family.
Also in 2014, Abaaoud persuaded younger brother Younes, then 13, to join him in the territory under control of IS.
Though Belgium has produced more radical Islamic fighters relative to its total population than any other European country, the departure of the boy, dubbed “Syria’s youngest jihadi”, made national headlines.
It also made Abaaoud a household name here.
Among other things, Abaaoud had been linked to the April attack on a church in the Parisian suburb of Villejuif in which a person was killed, and to an attack by a gunman on a high-speed train that was thwarted by three young Americans.
The next month, Abaaoud was quoted by IS’s English-language magazine, Dabiq, as ridiculing the inability of Western law enforcement to bag him.
He said he secretly returned to Belgium to lead the terror cell, then escaped to Syria despite having his picture broadcast across the news.