Bastille Day attack: The celebrations, the horror, and then the mourning

The words of French President Francois Hollande brought into stark relief the full horror of the indiscriminate, senseless murder on Bastille Day: at least 84 people killed, at least 10 of them children, who were up late to see the fireworks. 

Scores more youngsters were injured, many critically. It was, Hollande said on Friday, a "monstrosity".

"There are French among the victims and also many foreigners from every continent and many children, young children," said a clearly moved Hollande in a speech from a hospital in the French Riviera city.

"As I speak 84 people are dead, and around 50 are in a critical condition between life and death," he added. 

This was the horror left by of Mohamed Lahouaiej Bouhlel, who at 11pm local time on Thursday decided to drive his large white lorry into the crowd numbering up to 30,000 on the Promenade des Anglais - Nice's premier street where upscale hotels overlook kilometres of pristine beach. 

The 31-year-old French-Tunisian drove 2km along that route, zig-zagging into the crowds as they ran in fear. One witness said a motorcyclist tried to stop the rampage by drawing level with the truck and attempting to open the door before he fell and ended up under its wheels.

Bouhlel killed regardless of age, race, or religion before being brought to a stop in a hail of police bullets. In mere moments, the crackle of fireworks and gasps of delight had been replaced by the sound of gunshots and screams of the innocent.  

And when it was over, Bouhlel slumped dead in the lorry, its windows pock-marked by dozens of bullet holes, while dozens of his victims lay scattered on the street.

Hollande said what happened in Nice was undeniably a terrorist attack - the third mass killing in France in two years.

It comes after gunmen assaulted offices of the magazine Charlie Hebdo in Paris in January 2015, and the co-ordinated gun and bomb strikes on Paris that left more than 100 dead 10 months later.

Mourners gathered on Friday in Nice at makeshift memorials to relay their condolences to those killed. The Promenade des Anglais was almost silent, the beaches empty, the cafes closed.

Three days of mourning were declared, and shellshocked France once again found itself again counting its dead.

"France was struck on its national day... the symbol of freedom," said Hollande in a sombre televised address in the early hours Friday.

And as details emerged of the victims, the attack on France's national day broadened into an international incident: Two Americans, a father and a son from Texas, were among the dead. A Ukranian was killed, and a British citizen was confirmed among the injured. 

At least two Moroccans, an Algerian woman who attended the fireworks with her two children, as well a Tunisian national are also believed to be among the dead.

Reports stated that many French Muslims were likewise caught up in the violence, with 12 families losing loved ones.

In a Facebook video, witness Tarubi Wahid Mosta recounted the horror on the promenade.

"I almost stepped on a corpse, it was horrible. It looked like a battlefield," he said.

"All these bodies and their families ... they spent hours on the ground holding the cold hands of bodies dismembered by the truck. You can't even speak to them or comfort them," he said.

Another witness identified only as Nader told BFM television he saw the driver pull out a gun and start shooting at police.

"They killed him and his head was out the window."

The truck, which a police source said had been rented in the region "a few days ago", on Friday remained where it had been halted the night before, its front badly damaged and riddled with bullet holes and its tyres burst.

A source close to the investigation told AFP an "inactive" grenade was found inside the truck, as well as "several fake rifles".

One family lost their eight-month-old baby boy in the chaos but were reunited with him after they posted a desperate plea on Facebook.

World leaders rushed to condemn the bloodshed, with US President Barack Obama blasting "what appears to be a horrific terrorist attack".

Hollande announced he would extend France's state of emergency for three months in the wake of this latest attack and "step up" the government's action against Islamic State targets in Syria and Iraq

"We will continue striking those who attack us on our own soil," he said.

No one has yet claimed the latest attack.

The attacks in Paris last year were claimed by the Islamic State group, and in the national states of emergency that followed both "terrorist" cells were broken, and weapons and explosives seized.

The recent European football championship - long thought to be a prime target for IS - passed off peacefully, a credit to the French security services.

But the method of Bouhlel 's madness on Friday - the effective weaponising of an everyday object - has left many wondering how such horror can be prevented in the future.

As Patrick Skinner, an analyst from the Soufan group asked, how can you guard against such attacks? One cannot stop people driving trucks.