A fingerprint smudged on a Molotov cocktail, an identity card left in a getaway car and DNA found in a balaclava all helped French police piece together the identity of the jihadist gunmen who held the country in a three-day grip of terror.
On a near-freezing Wednesday morning, brothers Cherif and Said Kouachi got into their black Citroen loaded with an arsenal of heavy weapons and drove to the headquarters of the Charlie Hebdo magazine in central Paris.
Elsewhere close friend Amedy Coulibaly, 32, was preparing for his role in the bloodshed to come, to "take care of the police" while the brothers carried out an attack at the weekly to "avenge the Prophet Mohammed" it had so often mocked.
A few crucial mistakes would allow police to quickly identify them in a colossal manhunt that would culminate in a dramatic Friday showdown leaving all three dead.
An outcome they expected. Witness testimony and interviews to French television reveal Coulibaly wanted to "die a martyr" while Cherif said "we have got our vengeance", accusing the West of killing civilians in Iraq and Syria.
Charlie Hebdo massacre
After shooting a man in the entrance to the building, one of the gunmen -- who Paris prosecutor Francois Molins said was the brother Said, 34 -- entered a room where the entire editorial team was gathered.
Inside, veteran reporter Laurent Leger described hearing what sounded like "fireworks" before Said burst in, shouting "Allahu akbar" and spraying the room with bullets.
Leger hid behind a table as one by one his colleagues crumpled to the ground.
In a Paris restaurant, the girlfriend of Muslim policeman Ahmed Merabet, 42, was watching the horror unfold on television, unaware that her boyfriend was about to be coldly executed on a sidewalk.
The grisly scene inside the Charlie Hebdo building where eight journalists, a police guard and a visitor were killed revealed 31 Kalashnikov bullet casings, said Molins.
Outside some 25 bullet casings from a 9mm handgun were scattered around as the brothers climbed into their parked Citroen and fled to the north of Paris.
After an accident they were forced to abandon their car, which gave investigators crucial information such as Said's identity card.
Cherif's fingerprint was found on one of 10 Molotov cocktails, while Molins revealed police had also found a "jihadist flag" of the type used by Al-Qaeda in the Arabian Peninsula and Islamic State, two walkie-talkies, a Go-Pro camera and Kalashnikov cartridges.
That same afternoon police issued arrest warrants for the brothers and took Cherif's wife into custody.
Phone lines were tapped and search warrants obtained for houses where the suspects were likely to seek refuge as an all-night search resulted in different relatives being taken into custody.
Enter Coulibaly. The petty criminal believed to have become radicalised in prison was armed to the teeth when he was involved in a car accident before sunrise the next morning in Montrouge south of Paris.
Masked and wearing a bullet-proof vest, he fired on police coming to investigate with a Kalashnikov and handgun, killing a policewoman and injuring a municipal worker.
He hijacked a car, dropping his balaclava as he fled.
Within two hours police were able to match DNA from the balaclava with that of Coulibaly who was also identified by a witness and whose name had cropped up in the Kouachi investigation.
Cherif's wife confirmed to police the two men knew each other "very well" and she and Coulibaly's wife were found to have spoken by phone more than 500 times in the past year.
Betrayed by hunger?
Meanwhile the brothers, who had hijacked a new car, a Clio, popped back onto the police radar when they marched into a petrol station about an hour's drive north of Paris.
The duo placed what Molins called "war weapons" on the counter and stole a bag of food before again fleeing.
Helicopters and elite police spread out in the area in hot pursuit.
The suspects were again forced to show themselves when their Clio got stuck in the mud in a forested area after a rain-soaked day.
On Friday morning police received a call that two armed men had "jumped out of the woods" and hijacked a new car, telling the terrified driver they "were there to avenge the prophet", said Molins.
They fled back in the direction of Paris, where in the town of Dammartin-en-Goele they abandoned their vehicle when they ran into a police roadblock, where a shootout ensued.
With Said sustaining a light injury to his throat they fled on foot to a nearby printing business, taking the manager hostage but releasing him after he helped bandage the wound.
Unbeknownst to them, another employee, 26-year-old Lilian cowered under a sink one floor above, from where he was able to relay tactical information to police units outside.
Security forces left several messages on the brothers' cellphones in a bid to launch negotiations but went ignored, said Molins.
In eastern Paris, Franck was calmly shopping in the Hyper Casher Jewish supermarket when Coulibaly stormed through the door and opened fire.
Franck and a group of other people including a three-year-old and a one-month old baby were ushered into a refrigerator by a local employee to hide.
"We were all convinced we were going to die," he told AFP.
But Coulibaly soon realised some customers were hiding and sent someone to find them "threatening to kill them if they didn't return".
Molins said Coulibaly threatened to kill all the hostages if police launched an assault on the Kouachi brothers.
France breathes again
Outside the printworks, shortly before 5:00 pm, a door on the ground floor inched open for a few minutes before the gunmen burst out, guns blazing.
After failing to disorient them by throwing stun grenades, police forces cut them down. At the same time, a final assault was mounted on the supermarket where Coulibaly was also killed.
Inside the printing business, security forces found a loaded M42 rocket launcher, two pistols, 10 smoke grenades, two Kalashnikovs as well as a grenade on one of the gunmen's bodies.
Inside the supermarket they found about 15 sticks of dynamite, a detonator, a Kalashnikov and Russian-made pistols.
And France breathed again.