(CNN) -- It was a shooting spree that terrorized France for 10 days, and for weeks dominated the country's presidential election campaign.
Starting on March 11, Mohammed Merah, a 23 year old French-Algerian motor-bike riding assassin, who kept the visor on his helmet shut as he killed, and filmed every detail in high definition from a camera on his torso, shot four French paratroopers in two attacks, killing three and paralyzing one, and then on March 19 shot at point blank range three children and their teacher at a Jewish school in Toulouse, in an attack that shocked the world.
In an unprecedented manhunt, police tracked the killer to his apartment in Toulouse, where he held out during a two-day siege.During a seven-hour rambling confession to negotiators, he claimed to be acting on behalf of al Qaeda. He was killed in a blaze of gunfire as security services stormed the building on March 22.
Hours later Jund al Khilafah, known as JaK, an obscure Kazakh Jihadist group with ties to al Qaeda whose leaders are thought to be based in the tribal areas of Pakistan, claimed responsibility for the attacks.
"We claim our responsibility for these blessed operations," the group claimed, referring to the shooter as Yusuf al Firansi (the French) in an Arabic communiqué translated by the SITE Intelligence Group.
Counterterrorism officials initially treated the claim skeptically because the group had no track record of international terrorist operations.
But a senior U.S. counterterrorism official told CNN that Merah is now believed to have linked up with the Kazakh group just months before the attacks .
The U.S. official said there was "strong intelligence" that Merah spent time with the group in the tribal areas of Pakistan during a trip he made there between August and October 2011. "We're talking about a short time, perhaps even only an afternoon," said the official, who added that this did not necessarily mean the Kazakh group directed Merah to launch the shootings in France.
In the weeks after Merah's death there was much debate over whether he was an example of a "lone-wolf terrorist," plotting and acting alone, or had been recruited into the al Qaeda terrorist network, as he claimed to negotiators during the siege.
The reality, according to the senior U.S. official and a new book "The Merah Affair: the Investigation" set to be published in France next week, appears to be somewhere in-between.
French journalists Éric Pelletier and Jean-Marie Pontaut, who provided an advance copy of their book to CNN, reveal that Merah told negotiators during the siege that his handlers in Pakistan tasked him with assassinating an Indian diplomat in Paris. Merah claimed that on his return to France he rejected this mission, and instead decided to assassinate French soldiers to retaliate against the French military presence in Afghanistan. He claimed that on March 19 he only decided to attack the Jewish school in Toulouse after he discovered that the soldier he was targeting that day was not at home.
No evidence has emerged that Merah was in touch with jihadists in Pakistan after he returned to France in October 2011. He appears to have planned the attacks himself. French authorities have so far alleged the only other co-conspirator was his older brother, Abdelkader Merah, a radical fundamentalist long on their radar screen, who they arrested after Merah's death and charged with assisting in the plot. Abdelkader denies the charges, but according to the authors told French investigators he was proud of the way his brother died as a fighter.
The book outlines several reasons why French authorities began to take the claim by JaK, the Kazakh group, seriously. One was that Abdelkader Merah told investigators his brother liked to be called Yusuf -- the name JaK called him - by close family members, and this was only known inside the family. Another was they established that Merah had opened an Internet account under that name.
Furthermore, in a second statement of responsibility on March 31 a JaK operative revealed several pieces of information about Merah not then in the public domain, such as a trip he made to the Kurdish areas of northern Iraq, which were subsequently verified by French authorities, according to the book.
"The French think the claim is genuine: They don't have any doubt anymore," Pelletier said.
When Merah spent two weeks in the Miranshah area in North Waziristan in September 2011, a "major Western intelligence agency" had Merah on their radar screen, according to the authors. Electronic eavesdropping detected the opening of two Internet addresses in Miranshah that September, according to the authors, but Pelletier said it remained unclear at what point the agency established the account belonged to Merah.
It was only after the killings that French domestic security services were told that Merah spent time in North Waziristan during this period, according to the authors, raising the possibility that crucial intelligence that might have prevented the attack was not shared in time. When Merah returned to France from Pakistan in the fall of 2011, he was interrogated by domestic security agents who wanted to know the reason for his travel, but after he claimed his Pakistan trip was for tourism, he was judged as no immediate threat. Pelletier said it was not clear when France's foreign intelligence service was informed about his travel to North Waziristan.
After the killings, the Western intelligence agency informed French domestic security services that a number used by Merah in North Waziristan had also been used to contact terrorists belonging to Harakat al Mujahideen, a Kashmiri group with close links to al Qaeda, according to the authors, raising the possibility Merah was in touch with the group.
One of Harakat al Mujahideen's top commanders was Ilyas Kashmiri, a veteran Pakistani jihadist who in the two years before his reported death in a drone strike in June 2011 simultaneously played a lead role in orchestrating al Qaeda plots against the West, including a "Mumbai-Style" plot against Europe that led to an unprecedented U.S. State Department travel advisory for the Continent in October 2010, according to intelligence officials.
Pelletier said that this possible link to Harakat al Mujahideen may explain orders Merah apparently received to assassinate an Indian diplomat in Paris.
After the killings, French domestic security services learned that Merah received two days of "ultra-rapid" training in North Waziristan, according to the authors, after being vetted because of concerns he might be a spy.
JaK claimed it provided Merah with this instruction, after he reached their encampments.
"In Islamabad he came to know some people who took him to the Taliban and who, on their part, facilitated his arrival to the tribal areas, where he eventually ended up joining our brigade," one of the group's operatives calling himself Abu al-Qa'qa' al-Andalusi claimed in the March 31 statement in Arabic translated by the SITE Intelligence Group. Pelletier and Pontier wrote that subsequent investigations had confirmed Merah's passage through Pakistan's capital.
The JaK operative in the same statement described the nature of the training Merah received. "He did not desire to train in explosives, even though that was available to him within a very narrow circle of no more than three individuals. He preferred fighting with weapons, as he told me ... assassinations were more appropriate for him." The operative claimed the two of them conversed in French.
Al-Andalusi wrote that Merah nevertheless agreed to launch a suicide bombing attack in the Afghanistan-Pakistan border region but "one day after the program was changed for reasons that cannot be explained, Yusuf started his return to France, promising to accomplish what he is capable."
"Martyrdom was his goal and the hope that was always on his mind," he said.
JaK is believed responsible for several attacks against security forces in Kazakhstan, including the country's first suicide bombing and gun and grenade attacks, since its founding in September 2011, and has increasingly embraced al Qaeda's ideology of global jihad, Jacob Zenn, a Jamestown Foundation analyst who has researched the group said earlier this year.
Zenn said it is possible that a crackdown by security services in Kazakhstan has driven more of its members to the relative safe haven of the Afghanistan-Pakistan border region, where he said a few dozen of the group's members may have integrated with other jihadists.
Eyewitness accounts by European militants who traveled to the tribal areas of Pakistan suggest that lines have blurred between al Qaeda and other jihadist groups operating in the area.
Path to jihad
"The Merah Affair" sheds significant new light on Merah's radicalization, by drawing on interviews with family members, close associates and files kept on him by French security services.
The book paints a picture of a troubled truant from a broken home, who was impossible for his mother to control. For a time he was transferred to the care of social services. He spent hours playing "shoot-em-up" video games, and his adolescence increasingly turned to petty crime.
His father returned to Algeria when he was very young and his key influence became his older brother Abdelkader, a domineering Salafist fundamentalist who also had a history of petty crime, according to the authors.
After being imprisoned in January 2008 for a knife assault, Merah was born again into Islam through contact with other Muslim prisoners, according to fellow inmates. One of them claimed Abdelkader Merah played a central role in his radicalization in prison by supplying him with recordings of jihadist chanting, which Abdelkader Merah's lawyer denies, according to the authors. The book reveals that Merah found prison life difficult and once attempted suicide.
Abdelghani Merah, one of Merah's older brothers, told investigators that his brother had become radicalized by the time he was released from prison in September 2009, and began to express his rage over the presence of French troops in Afghanistan, the book reveals. His mother told investigators that for a period he hung out with radicals in the Toulouse area.
Mohammed and Abdelkader Merah had first came on the radar screen of French counterterrorism officials in the mid-2000s because both were loosely connected to a group of extremists in the Toulouse area that was recruiting militants to fight in Iraq, according to the authors. In 2011, Abdelkader Merah even arranged a short-lived marriage between his mother and the father of Sabri Essid, one of the convicted facilitators, who was sentenced to a short time in prison in France after being detained in Syria in 2006.
Abdelghani Merah, the other brother, who had become estranged from Abdelkader Merah after the latter sharply disapproved of his marriage to a Jewish woman, told investigators that Mohammed Merah was a subservient side-kick to Abdelkader Merah when they were growing up, according to the authors. "Abdelkader rottened the life of Mohammed," Abddelghani Merah said. "It was him, I'm certain that gave the idea to Mohammed."
Mohammed Merah's radical activity was escalating. In June 2010 Merah forced a 15-year-old boy to watch violent jihadist propaganda, including the execution of American hostages, according to a complaint made to the police at the time by the youth's mother, according to the book. After he learned she had filed a police report, he threatened her and punched her son, according to her account. She told a French newspaper that he told her he was a Muhajid and would die a martyr.
During the siege, Merah claimed he had been trying to participate in jihad for several years. In early summer 2010, he tried to enlist in the French Foreign Legion, but was rejected. According to Pelletier and Pontier, he told negotiators his plan had been to turn his guns on his fellow soldiers once in Afghanistan, and join the Taliban insurgency. Between July and October 2010 he traveled to several Middle Eastern countries, including Syria, Iraq, the Palestinian territories, Israel and Egypt, where Abdelkader Merah was spending some time pursuing religious studies. His brother later told investigators that Merah confided details of his trip to him during his stay. He envisaged at that time fighting jihad in Somalia or Sudan, according to the authors.
"I now realize that he was searching a for a way to get the contacts he needed to join al Qaeda and meet an emir who could decide what he should do. To commit the acts which he did, you have to get the sanction of a sheikh or emir," Abdelkader Merah later told investigators, according to the authors.
After briefly returning to Toulouse, Merah set off for Afghanistan via Tajikistan. His plan, he later said during the siege, was to get himself kidnapped by the Taliban and then persuade them he shared their views so he could join their ranks, the book revealed. The plan failed: Merah was apprehended in Kandahar in November 2010 by Afghan police before he could connect with militants, and briefly transferred to American custody. But Merah had entered Afghanistan lawfully and there were no grounds to detain him, so he was allowed to return to France.
Increasingly on the radar screen
It was only when he was back in France in January 2011 that he answered the police summons in relation to the altercation with the French youth the previous summer. He told police he was not an extremist, and the complaint was false, according to the authors. After the plaintiffs indicated they did not want to see him do prison time, police told him he was free to go.
But his trip to Afghanistan had placed him more firmly on the radar of French domestic security services. They wiretapped his phones, but after finding no incriminating evidence, ceased listening to his phone conversations in April 2011 as they were legally required to do, according to the authors.
The security services continued their human surveillance of him, logging 1,200 hours by August 2011 and installing a surveillance camera in front of his apartment building, according the authors. But Merah showed no signs of radicalism, nor did he have any contact with extremists in the Toulouse area.
His life did not seem out of the ordinary. To support himself he was working as a mechanic in various vehicle repair shops as well as receiving French welfare payments, according to the authors.
He managed to slip away to Pakistan in August without French security services noticing.
When security services learned that month that he had disappeared, French domestic security officials contacted his mother, who told them he had left for Pakistan in search of a wife, according to the book. The security services told her to tell him they wanted to see him on his return to France.
Merah soon called them back from Pakistan, promising he would get in touch with them as soon as he returned to France. He was true to his word. After a brief spell in hospital because he had contracted hepatitis A during his travels, he met with them and allayed their concerns, according to the book.
In the months that followed he did not seem like a man on a mission. In December 2011 he married a 17-year-old French Muslim who wore the full veil, but they quickly divorced, according to one of his fellow mechanics, because she did not take care of the housework, the book revealed.
Several months later, Merah carried out the shootings. According to the authors, he tracked down the first paratrooper he shot by searching for the terms "soldier" and "motorbike" online on his mother's computer, which took him to an online ad posted by a French paratrooper selling his motorbike. After the two arranged to meet, he shot the paratrooper, making sure he was dead with a final shot at point blank range.
In a brilliant piece of lateral thinking, it was by exhaustively cataloging who in France had searched these Internet search terms that French police were led to Merah, according to Pelletier and Pontier. CCTV footage at the scene of the second paratrooper shooting had also revealed which type of motorbike the assassin was driving, and the police became almost certain Merah was responsible when investigations established Merah was driving this type of model, the book revealed.
After his death, police found a thumb drive in Merah's trouser pocket with a file named "Al Qaeda Attacks France" which contained video of his shootings set to jihadist music. He had already sent a copy to al Jazeera offices in Paris. The network decided not to air it.