Holed up in a printworks and surrounded by police, killers Said and Cherif Kouachi were unaware that commandos were being tipped off about their every move.

For, hidden in a cardboard box just yards away was 27-year-old Lilian Lepere.

And he was able to alert police about the location of the gunmen and the layout of the building.

For more than six hours the graphic designer passed on crucial information until the siege ended in a bloody shootout as the terrorist brothers, who had vowed to die as martyrs, burst out from their lair all guns blazing and were mown down in a hail of bullets.

Police commandos stormed the print works where the Charlie Hebdo gunmen were holed up with a hostage and the terrorist brothers burst out from their lair all guns blazing

A huge ball of fire erupted amid gunfire and explosions as French special forces shot dead the two Charlie Hebdo gunmen

From inside his claustrophobic hideout, Mr Lepere had first sent a text message to his father when the Kouachis took over the print works at Dammartin-en-Goele, a small town just north of Paris.

He wrote: ‘I am hidden on the first floor. I think they have killed everyone. Tell the police to intervene.’

It is understood he was in a locked room. He continued to provide vital information to police and special forces via his phone as snipers took up position on surrounding rooftops and helicopters buzzed overhead.

Lilian Lepere, 27, hid in a cardboard box as the Charlie Hebdo gunmen held a father-of-two hostage for eight hours

Mr Lepere emerged unscathed from the shootout and was taken to a psychological assessment unit where it is understood he was to be reunited with his family last night.

A hostage held at gunpoint by the terrorists was also freed. The Kouachi brothers had been on the run since killing 12 journalists and police officers in a terror raid on the offices of satirical magazine Charlie Hebdo in Paris on Wednesday.

As the huge manhunt for them continued, they dumped their stolen getaway car and fled on foot into a forest 50 miles north of the capital.

This morning they managed to evade the huge police dragnet and just after 8am hijacked a grey Peugeot 206 being driven by a woman teacher near Montagny-Sainte-Felicite, 30 miles north-east of Paris. Jean Paul Douet, the mayor of the village, said a colleague saw the men force the woman into the back seat.

‘She saw their weapons, and in particular their rocket-propelled grenade launcher,’ he said.

The teacher was freed unhurt soon afterwards, then dozens of police cars began chasing the fugitives along the N2 highway towards Paris. During the chase, shots were exchanged.

The brothers dumped their car and fled on foot to a family-run printing company on an industrial estate in Dammartin-en-Goele.

They burst into the business – posing as armed police – and took the company’s boss hostage.

Armed police surrounded the building and sealed off the town of 8,000 people.

All businesses closed, nearly 1,000 children were evacuated from schools and the streets were left deserted except for lines of police vehicles and units of heavily armed officers clad in combat gear. Masked and helmeted troopers with automatic weapons were seen peering out of a blue helicopters buzzing overhead.

Michel Carn, a resident, said: ‘The whole zone is surrounded. We are confined to our homes.

‘We can hear helicopters and there’s one currently hovering over my house.’ With so many low flying police and army helicopters, some flights were unable to land at Paris’s main Charles de Gaulle airport seven miles away.

Incredibly, a salesman visiting the small print works office minutes after the gunmen seized it described an encounter with one of the fugitives – and even unwittingly shook his hand. ‘When I arrived my client came out with an armed man who said he was from the police,’ said the man, who gave his name only as Didier.

Al Qaeda brothers Cherif (left) and Said Kouachi were both shot dead by police as they tried to fight their way out of the industrial building

The graphic designer was able to alert police about the location of the gunmen and the layout of the building

French special forces sharp shooters on a rooftop at the scene of the bloody siege which saw both brothers mown down in a hail of bullets

‘My client told me to leave so I left. I was in front of the door. I shook [my client] Michel’s hand and I shook the hand of one of the terrorists.’

He said the black-clad man who was wearing a bullet-proof vest and carrying what looked like a Kalashnikov rifle told him: ‘Leave, we don’t kill civilians anyhow.’

He said: ‘That really struck me, so I decided to call the police. I guess it was one of the terrorists.’

As the standoff continued, police attempted to negotiate with the brothers but were told: ‘We are ready to die as martyrs.’

Officers also scrambled phone signals after the terrorists reportedly called with a criminal associate.

As the siege continued, the town mayor’s office appealed on its website for residents to stay behind closed doors. Many workers were forced to stay huddled inside their offices and shops because it was too risky to venture onto the streets.

The gunmen's hostage, named as the company's director Michel Catalano (circled), is believed to have been rescued alive

Mr Lepere's family and friends knew he had gone to work and tried in vain to reach him between 9 and 11am by phone and on Facebook

A police helicopter hovers over Création Tendance Découverte, on an industrial estate outside Paris

French gendarmerie intervention forces arrive at the scene in a Dammartin-en-Goele industrial zone

One of the pupils inside the Dammartin-en-Goele high school said by phone from inside, ‘We are scared’, adding: ‘We’ve called our parents to make sure they’re OK.’

A 60-year-old woman said her daughter worked close to the hostage scene. ‘My daughter told me, “Don’t be scared mummy, we’re well protected”.

She was calm but me, I’m scared. I’m really scared,’ the woman said, sobbing. The siege ended at just after 3pm, as dusk fell.

Commandos crept on to the roof of the building and set off a series of explosions before colleagues stormed in. At least two military helicopters containing special forces landed on the factory building, another in the grounds.

Members of the GIGN (National Gendarmerie Intervention Group) hovering in a helicopter at the dramatic siege involving Charlie Hebdo gunmen

Defiant to the end, the terrorist brothers charged out firing Kalashnikovs at the security forces before being shot dead.

Teenager Atlantis Farina, who lives close to the scene, was returning home when he heard explosions.

‘The ground here started shaking, that is what shocked me most,’ said the 17-year-old.

‘Then there was lots of what sounded like gunfire, it sounded like the suspects were firing back at the police. ‘There was smoke too – like they had thrown a grenade. ‘I am so glad it is over, it brought panic to the area. My mum was very worried, and I was quite scared too.’

Residents living closest to the printworks had been evacuated from their homes minutes earlier, sparking fears the terrorist may have had bombs.

Alan Linck, a teacher who lives less than 100 yards from the scene, said: ‘They told us all to go.