By Paul Cruickshank, Tim Lister and Per Nyberg
He was the father of two small children and lived an ordinary life in a drab English town. Most of his family, originally from Iraq, had settled peacefully in Sweden. But unknown to any of them, Taimour Abdulwahab had embraced jihad - and was planning to blow himself up among Christmas shoppers in the Swedish capital.
Abdulwahab's last steps and contacts offer further evidence that "the lone wolf" terrorist is very difficult to identify. But they also show that - even with training - the lone suicide-bomber faces serious challenges in carrying out an attack.
Abdulwahab flew to Sweden from Luton, England on November 19 last year - on the last stage of a journey to his own death. He went to stay with his family in Tranas, a quiet town known for its golf and fishing set amid rolling hills some 100 miles from Stockholm. He spent the next few days with his sister and parents at the family apartment.
But somewhere nearby he was building a powerful if rudimentary bomb, using ingredients he was able to purchase in the town: pressure cookers, fireworks, explosive chemicals and nails and ball bearings. According to British investigators, he had already bought pollen presses and herb grinders in Luton that could be used in bombs.
Abdulwahab, it seems, was working alone - but he was no amateur. Like other confessed terrorists in the United States and western Europe, he had received bomb-making training - not in Pakistan, like many others, but in Iraq. According to sources in Sweden, at least two others may have been familiar with his plans if not actively involved in the plot.
Swedish prosecutors tell CNN that after nearly three weeks in Tranas, Abdulwahab walked out of the family apartment on a sunny Saturday morning. It was December 11, 2010.
"When he left his apartment he wasn't carrying anything - no suitcase or bags. His parents thought he would come back later that afternoon," said Agnetha Hilding Qvanstrom, a senior official in Sweden's Public Prosecutor's Office for National Security.
Qvanstrom told CNN investigators had interviewed 800 people, conducted searches of several premises, and recovered CCTV footage while retracing Abdulwahab's movements. But they were unable to account for 40 minutes on that fateful Saturday.
"We don't know where he went during that period," Qvanstrom said. Investigators believe he may have gone to retrieve his partially-built devices but have not yet located where they were hidden.
Shortly after noon, Abdulwahab left Tranas in a white Audi he had bought after arriving in Sweden. For a man of modest means, he did not seem short of funds. The vehicle's GPS system helped Swedish investigators subsequently retrace his route, which included a stop at a gas station. CCTV footage showed that as he left his car and went into the restroom he already had a bomb strapped to him.
"For a thin guy, he suddenly had quite a stomach - it seems a bomb on his stomach. It may have been that he was fixing something in the men's room," Qvanstrom told CNN.
A couple of hours later, Abdulwahab parked on Olof Palme street - in an area of Stockholm full of stores and apartments. Sitting in his car, Abdulwahab sent several e-mails in English: to a Swedish news agency, the Swedish security services, his wife back in Luton and his mother in Tranas, according to Qvanstrom.
"He said it was because of Lars Vilks and the Swedish presence in Afghanistan," Qvanstrom, told CNN. Vilks, a Swedish citizen, was one of the cartoonists who in 2005 drew a controversial depiction of the Prophet Mohammed. The publication of the cartoons caused outrage across the Muslim world, with riots in Pakistan and Libya. And they have been cited by many militants as driving them toward violence.
At 4:50 p.m. Stockholm police began receiving calls about a car on fire in central Stockholm. Qvanstrom told CNN: "Our theory is that he put the car on fire to draw people close."
Then he planned to use a walkie-talkie to set off a device inside the car. As people ran from the scene, "they would run towards the bomber, who would then set off the explosive devices he was carrying on his body," Qvarnström said.
Forensic examination of the car showed it had been set on fire using several cans of gasoline, bottled cans of gas and fireworks. An explosive device had also been placed on the passenger seat, made from a pressure cooker and similar to the two explosive devices the bomber carried on his body. A second walkie-talkie was also found in the car.
But the explosives in the car did not detonate. CCTV video showed that in a nearby street Abdulwahab was trying to blow himself up. For ten minutes he walked through the area, trying to make the device attached to his stomach work.
Just before 5 p.m. part of the bomb finally exploded, killing Abdulwahab instantly. But the rest of the device didn't explode, potentially saving many lives.
Swedish investigators say the bomb in his backpack was substantial – "a pressure cooker filled with 4-5 kilos of explosive substances, along with six aluminum bottles which together held some 5-6 kilos of explosive substances.
"On his front, he carried another pressure cooker filled with 4-5 kilos of explosives, and 9 so-called pollen presses, weighing roughly 2 kilos. In all, the pollen presses contained slightly less than 500 grams of explosives."
A Swedish counter-terrorism source told CNN the pressure cookers were each filled with ammonium nitrate, an explosive chosen by al Qaeda in plots in the West and by far-right extremist Anders Breivik who has admitted carrying out a terrorist attack in Norway in July.
"The explosive devices, had they gone off, were powerful enough not only to cause injury to people and property but also to kill people," said Anders Danielsson, head of the Swedish Security Service.
Magnus Ranstorp, research director at the Swedish National Defence College and a leading counter-terrorism expert, told CNN that while the devices were made from simple ingredients and simply constructed, they were anything but amateurish.
"My understanding is that there was a level of sophistication in the detonation mechanisms and the wiring, " Ranstorp told CNN.
Swedish authorities continue to investigate whether Abdulwahab was linked to terrorists overseas, or received help in carrying out the attack.
"We don't know if he got help in Sweden. What we do know, is that we really think he was alone this day in Stockholm, but we don't know if anyone tried to help him before to buy ingredients for bombs," Qvanstrom told CNN.
But Abdulwahab was in contact with someone in Iraq the day of the failed attack. According to British investigators, Abdulwahab made and received a telephone call to a mobile number in Iraq. They say he had traveled to Syria and Iraq in 2009 to receive training. The head of Iraq's counter-terrorism unit, General Dhai Kanani, disclosed last January that a detained al Qaeda suspect had confirmed that Abdulwahab received three months bomb-making training in Mosul, a stronghold of the Islamic State in Iraq, successor to al Qaeda in Islamic Mesopotamia. And the first photograph to emerge of Abdulwahab after his death was on a jihadist website, showing a slim, smiling young man with what may be the hills of northern Iraq behind him.
"The sophistication of the wiring seems to strongly suggest that he was not a self starter or lone wolf, even though he carried out the attack by himself," Ranstorp told CNN.
He pointed out that Abdulwahab tried to radicalize others in Luton in the years leading up to the attack.
Ranstorp says there are still gaps in Abdulwahab's story. Given his lack of employment, it's still unclear how he found the resources for his suicide mission. And investigations continue into possible accomplices, or others that may at least have been aware of his intentions. Another man, Nasserdine Menni, who had been living in Glasgow, faces charges that he supplied money to Abdulwahab and that they conspired together "and with others to further terrorist aims by criminal and other means." Menni's next court appearance is in January.