Like the Boston bombing in 2013, the 'Charlie Hebdo' massacre has come to a tale of two brothers.
The relatively short lives of Cherif (32), and Said Kouachi (34) ended in a blaze of gunfire as they got their wish to go out as "martyrs" to their cause in a firefight that was watched by the world.
Their terror-reign ended only after the biggest manhunt in French police history.
The brothers were French. They were born to Algerian-born parents in Paris, a few blocks from the scene of Wednesday's savage attack. As small boys they were brought up in a children's home in Brittany.
Cherif, especially, was well-known to French security. He has served two periods in prison after being linked to an Islamist network which sent fighters to Iraq from 2003-06.
Yet despite the widespread reports to the contrary, he does not appear to have fought, or received training, abroad. Although under surveillance, he was regarded by French internal security as a low risk "has-been".
Awkward questions will inevitably be asked about the failure of anti-terrorist agencies to spot the brothers as a serious threat.
The explanation seems to be that Cherif was regarded as "too old" - a failed wannabe jihadi, who had reverted to the chaotic existence of his early 20s.
Said, though older, has always been in Cherif's shadow. He had never been seen as any sort of threat.
All French security's efforts have been focused in recent months - with some success - on preventing domestic acts of terror by jihadis returning from Iraq and Syria. These men, mostly in their teens or twenties, are often recent recruits to the cause and, in some cases, recent converts. Cherif, and therefore Said, were overlooked as they belonged to a previous generation of home-grown extremists.
Cherif, according to Vincent Ollivier, his former lawyer, went into his first prison term in 2006 as confused kid and emerged as a physically stronger radical. One of the Islamists with whom he consorted in jail was Salim Benghalem, now regarded by the US as a principal organiser of Isil in Syria.
All this would seem to beg the question - Was Wednesday's attack an Isil operation? French security officials - perhaps covering their embarrassment - believe it was more likely a freelance attack, inspired by Isil, but not directly ordered or controlled from the Middle East. They were describing the brother's yesterday as a "family terrorist cell".
The 'Charlie Hebdo' assault was a bizarre mixture of chillingly professional and chaotic. The gunmen were calm, ruthless and heavily armed. On the other hand, they were extraordinarily feckless. They were rapidly identified as suspects when Cherif left his identity card in the car they crashed a mile from the massacre. They had initially tried to storm the wrong building. And on Thursday, rather than lying low, two men identified as the brothers pulled into a rural petrol station in the Aisne and ordered their car to be filled at gunpoint.
The Kouachis do not have the typical profile of converts to radical Islam. Aged four and two, they were placed in a children's home in Rennes before being fostered by a local family, who had converted to Islam.
Cherif qualified as a sports teacher and worked briefly in Rennes - a 2005 Facebook post shows him rapping. The brothers moved to Paris and then the northern suburb where they became involved in petty theft and drug dealing. Ollivier remembers him in his early 20sas "an apprentice loser in a baseball hat". "He smoked, drank, wore no beard and had girlfriends," the lawyer said. "He was a confused kid who did not know what to do with his life and then, overnight, met people who persuaded him that he was important."
Cherif was first radicalised, said Ollivier, by the US-led invasion of Iraq. He was especially outraged by the images of mistreatment at Abu Graib prison. Even then, Ollivier said, Cherif recruited others but did not go himself, knowing that few foreign recruits lived long. He was convicted in 2006 of aiding and abetting a terrorist organisation and sentenced to 18 months in prison - a term which he had already served on remand.
In 2010, he was arrested and served another six months on remand on suspicion of belonging to jihadi group trying to spring a leader from jail. He was rereleased without trial after persuading investigators he had joined the group -and travelled to an alleged Auvergne training camp - only to "play football".
Cherif appears then to have dropped off the security services' radar. Said scarcely merited a blip on their screens.
Authorities believe the 'Charlie Hebdo' attack had been long planned by Cherif. If so, why? What turned the jihadi "has-been" into a brutal killer? Was he guided from the Middle East?
It will be some time before such answers can be answered. Ask French Algerians what they think of the events of the last few days, and there is no hesitation in their answers.
Sheltering from a shower in the stairwell of a tatty high-rise in the Paris suburb of Pantin-Aubervilliers, Alim was spending yesterday much as he passes most days - looking for a job and wondering whether he can have a future. The 20-year-old is one of thousands of French-Algerians living in the northern banlieues of the capital, where the unemployment rate is up to four times the national average of 10pc and social schism erupts sporadically into disorder and occasional riot. It is here that Cherif and Said Kouachi, the two brothers suspected of murdering 12 people at the offices of 'Charlie Hebdo', fled 24 hours earlier. Like many of his peers, Alim has little time for the police, or les flics, who he says are racist and guilty of oppressive random document checks.
But he has even less time for the Kouachi brothers, who were radicalised around 2003 while living on the other side of the Paris ring road in the neighbouring 19th arrondissement. Spitting on the ground in disgust, he said: "These guys were dangerous. And they're also fools. What do they think this will do for Muslims in France? What will it do for people like me when we already have a hard time getting work?
"What happened was disgusting. A lot of guys around here are angry about living here. We don't like the police: they give us a hard time. But it's another thing walking into an office and killing people just like that in the name of God. It's not my God or anyone else's around here." (© Independent News Service)