As the sun came up once more people began to walk quietly over the pavements where just hours before dozens of torn bodies lay. The broken benches, the discarded pushchairs, the detritus of carnage and panic had been cleared away and the tarmac washed clean. The only tangible reminder of the horror which had taken more than 80 lives was the memorial shrine, thousands of bunches of bright flowers piled in front of the Palais de la Mediterranee hotel where the lorry had finally ended its trail of carnage and the killer died - ‘neutralised’ in the authorities' argot - in a hail of police bullets.

As Nice attempted to return to a normality it would never again achieve, the questions and the accusations began. How was it that the 31-year-old Mohamed Lahouaiej-Bouhlel, who had joint French and Tunisian citizenship, was able to evade the security barriers and the police officers who should have been safeguarding the 30,000 people on the Promenade des Anglais, celebrating Bastille Day, the day in 1789 when the French revolution began with the storming of the infamous Paris prison.

One report claimed that Lahouaiej-Bouhlel told officers that he was delivering ice creams and was let through. Another report maintained that security was virtually non-existent, only 62 National police and 50 Municipal officers were on duty when there should have been 700.

Certainly, on the eve of the celebration Christian Estrosi, president of the regional council, had sent a letter to President Hollande in the Elysee Palace alleging that the national force was in severe crisis. Estrosi, a Republican opposed to the socialist administration, would, of course, be keen to portray Hollande and Prime minister Manuel Valls as weak on security.

There had been a mood of celebration on the Nice seafront on Thursday at the end of a day of celebration. It had culminated, the crowd thought, in an air force fly-past and a fireworks display. But a few streets away a 19-ton white lorry was driving erratically, speeding, braking, speeding up again. But it was not for another half hour before the attack began.

Lahouaiej-Bouhlel, a delivery driver, had hired the vehicle on Monday in nearby Saint-Laurent-du-Var. Now, at 10.30 at night with the promenade bustling, families with their children, couples linking arms and laughing together, it began. The lorry doubled back from the direction of the airport, came through the barriers opposite the Lenval children’s hospital, creeping forward from house number 11 on the promenade, accelerating, zig-zagging to mow down the maximum number of panic-stricken promenaders, not stopping until it reached house number 147, more than a mile away.

Almost at the start of the mile-long death charge witnesses report that the driver began shooting at two police officers, who fired back. A motorcyclist gave chase and tried to leap onto the truck, but fell under the wheels. Last night he was still critically ill in hospital.

This only spurred Lahouaiej-Bouhlel to press harder on the accelerator, careering into families listening to an orchestra, swerving onto the pavement and back onto the road, ploughing into people as he went, knocking them over like skittles, in the words of one eyewitness.

Whether the truck broke down or he decided to end it all by getting out of the cab and shooting as many as he now could, or whether he stopped to shoot a man who jumped out of the crowd in front of the lorry, he moved across into the passenger seat, which is where his life ended in a hail of bullets from police who surrounded the vehicle.

Strewn along the palm-tree lined road behind lay 84 dead, 10 of them children, 202 injured, more than 80 of them critically.

There is no evidence, yet, that this was planned by Islamic State, although it was clearly inspired by them, their media group claiming that the killer was one of their ‘soldiers’. Their statement suggested that he had acted independently, “in response to calls to target the citizens of coalition countries fighting the Islamic State”.

He certainly fitted a recognisable pattern, a violent petty criminal, a loner who had no time for his neighbours in the modest block of flats he lived in, one of whom described him as looking a bit like George Clooney. He was estranged from his wife after she threw him out after an assault. In March police arrested him for hurling a pallet at another driver. He was given a suspended sentence and made to contact police once a week.

But although he was clearly known to police he was unknown to France’s disparate and unco-ordinated security services. Neither was he on the files of the intelligence agencies in Tunisia, where he was born. He did not seem overly religious, was not known as belonging to any jihadi group, he drank, eyed up women living around him in the Quartier des Abattoirs, liked salsa music, dressed casually, often in shorts and work boots, he seemed just one of the many 40,000 French-Tunisians in Nice - until he pressed down on the accelerator on the Promenade des Anglais, named after an 18th Century English parson who paid for it, and became a byword for mass murder.

A multitude of questions remain, principal among them is how he acquired the stash of weapons found in the lorry? And was he acting alone? As tearful mourners ended a vigil on the promenade yesterday police were launching a series of raids. Five people are now in custody, including Lahouaiej-Bouhlel’s estranged wife. But perhaps the most important question remains unanswered. Where next?