The gunmen behind France's worst terrorist attack in decades appear to have been easy prey for recruiters to violent jihad.
The children of immigrants, with seemingly chaotic family lives, they were frustrated by injustices they perceived around them and had been trying to make their way with few means, according to court records and experts who study terrorism networks.
"These were people who were marginalized, who broke with society. They went to prison, and they became radicalized because they needed to be heroes," said Christophe Crepin, spokesman for a French police union. "In the end, they're just barbarous assassins."
Their path to radicalization began in the seething immigrant neighborhoods on the edges of Paris.
Said Kouachi, 34, and his brother Cherif, 32, were born to a family of Algerian descent in Paris' 10th arrondissement. Their father appears to have been largely absent, and their mother struggled to raise the family's five children, Crepin said.
The brothers were placed at a young age in a center for orphaned and troubled children outside the capital. Their mother died soon after.
The pair returned to Paris around 2000 and moved into an apartment in the 19th arrondissement, an area heavily populated by migrants from France's former colonies in North Africa. They survived on odd jobs. Cherif Kouachi delivered pizzas for a time and later worked at a supermarket fish counter, according to French news reports.
Long before the brothers stormed the offices of the French satirical magazine Charlie Hebdo on Jan. 7, killing 12 people, they fell under the influence of a self-proclaimed Islamist preacher they met at a local mosque.
Still in his 20s and working as a janitor, Farid Benyettou became the mentor and spiritual leader of a group of young Muslims who were angered by images of American abuses at the Abu Ghraib prison and wanted to go fight U.S. soldiers in Iraq. French authorities called them the Buttes-Chaumont network, after the picturesque park with its picnickers and hilltop views where they would go jogging.
Benyettou was just a year older than the younger Kouachi, but the brothers looked up to him because he claimed to have studied Islam and had a brother-in-law who was part of an Algerian militant group, said Jean-Charles Brisard, chairman of the Paris-based Center for the Analysis of Terrorism. They attended lessons at Benyettou's apartment, where they discussed the religious arguments for waging holy war.
Even then, Cherif Kouachi would talk about wanting to stage an attack in France, a friend told investigators. But their mentor told them the fight was elsewhere.
Some members of the Buttes-Chaumont group would later be killed in Iraq or return badly maimed, but the Kouachi brothers never made it to the war. Cherif Kouachi was arrested in a 2005 crackdown on the network that was funneling fighters. He had a plane ticket for Syria, then the gateway for fighters hoping to do battle against the U.S. in Iraq. His brother's role in the network, if any, is unclear.
At the time, the younger Kouachi told investigators he was relieved to be caught. He described himself as a "ghetto Muslim," according to the French newspaper Le Monde, a clean-shaven hipster who liked to rap and smoke marijuana with friends. He didn't want to die in Iraq, he said, but was afraid he would be called a coward if he didn't go.
Prosecutors thought he had been manipulated by a cult-like ideology and didn't consider him a serious threat. When the case wrapped up in 2008, he was sentenced to time served.
But the radicalization that had begun on the streets of Paris intensified in prison, experts say. Remanded after his arrest to Fleury-Merogis Prison south of Paris, the nation's largest, he found himself in the company of hardened extremists.
There he met the Algerian-born Djamel Beghal, regarded as one of Al Qaeda's top recruiters in Europe, and convicted in a 2001 plot to bomb the U.S. Embassy in Paris. With them was the Kouachi brothers' future accomplice, Amedy Coulibaly, serving time for one of a string of robberies.
Coulibaly, the same age as Cherif Kouachi, was born in France to parents of West African descent. The only boy in a family of 10 children, he grew up on a housing estate in Grigny, south of Paris, that is notorious for gangs, drugs and violence.
"These guys are looking for something to join, they're looking for something to identify with," said Andrew Liepman, a senior policy analyst at Rand Corp. and former principal deputy director of the National Counterterrorism Center. "It could be a bridge club, the Boy Scouts or Al Qaeda — and there aren't a lot of bridge clubs in prison."
Cherif Kouachi and Coulibaly would later be named in a plot orchestrated by Beghal to free another Algerian-born militant, Smain Ait Ali Belkacem, who was sentenced to life in prison for his role in the 1995 Paris subway bombing. A judge ruled there was insufficient evidence to convict Kouachi in the case, but Coulibaly was sentenced to five years in prison for supplying weapons to carry out the 2010 plot.
Court documents, including surveillance reports and judicial interviews, show the influence that Beghal had over Coulibaly and Kouachi.
After his release in 2009, Beghal kept in close contact with his followers. Coulibaly, sometimes accompanied by Kouachi, was a regular visitor to the town of Murat in south-central France where Beghal was placed in a hotel under police supervision while appealing extradition to Algeria, the documents show.
In April 2010, a small group that included the younger Kouachi was observed exercising and taking a walk in the forest with Beghal.
Coulibaly's partner, Hayat Boumeddiene, who married him in a religious ceremony that is not recognized under French law, sometimes joined the men on these visits. French newspapers published a photograph of her in the countryside pointing a crossbow at the camera while dressed in a face-covering veil.
There were also frequent phone calls in which Beghal appeared to be providing religious instruction to the men.
In one exchange recorded from wiretaps, he encouraged Coulibaly to donate money to a "brother" who was helping Palestinian children, telling him that they were the "combatants of tomorrow, those who are resisting the Jews."
With hindsight, Coulibaly's reply is chilling. "I'll also do that, God willing," said the man who would later gun down a female police officer and four hostages at a kosher market.
In another exchange, Coulibaly asked Beghal whether it was permissible for people to leave debts when they die. Beghal told him that in principle, all debts needed to be paid, but added that exceptions were possible.
When investigators searched Coulibaly's home in 2010, they found 240 rounds of ammunition that could be used in Kalashnikov assault rifles. He admitted that the bullets belonged to him but said he intended to sell them and was not aware of any plans for an attack or prison break.
"I'm the village idiot in all this. I don't know anything," he told investigators. "I wasn't going to go free a guy I don't even know. Honestly, I've done some stupid things but there are limits."
Asked about his relationship with Beghal, he said, "He's a person who touched me."
"At the moment, his situation isn't comfortable, because he has no revenue and that makes me pity him," court records quote him as saying.
Coulibaly would prove to be a model prisoner, said Crepin, the police union spokesman. After his release last year, he moved back in with Boumeddiene and the pair fell off the police radar.
In 2011, U.S. intelligence officials tipped off their French counterparts that Said Kouachi might have gone to Yemen for training with Al Qaeda's local affiliate. They are now looking into the possibility that Cherif Kouachi traveled on his brother's passport.
Both brothers were placed under police surveillance. But as months went by, no evidence emerged that they were involved in anything sinister, authorities said. The police turned their attention to people they viewed to be of more immediate danger — with deadly results.