One moment, the famous Nice waterfront boulevard was packed with people watching Bastille Day fireworks exploding over the Mediterranean.
But in the next horrific seconds, a truck rammed into the crowd at high speed, leaving a trail of bodies, shock and despair through a French Riviera fiesta.
It would be difficult to pick a more meaningful time to attack France, as the assailant did, on the country's national day. The terrorist, whose vehicle contained guns and grenades, targeted a city full of flags and fireworks celebrating independence day, a day about revolution and the casting off of the yoke of a king.
Last night the death toll stood at 84. Many children were among the dead. At least 18 people were critically injured and dozens more were also hurt.
As police and troops counted the bodies along the Promenade des Anglais, people in France were coming to grips - again - with the fact that the entire country could become part of the front line with the Islamic State as its "caliphate" in Syria and Iraq starts to collapse.
"The horror, the horror has, once again, hit France," President Francois Hollande said in a nationally televised address, just hours after the attack. He said the "terrorist character" of the assault was undeniable, and he described the use of a large truck to deliberately kill people as "a monstrosity".
Interior Minister Bernard Cazeneuve said: "We are at war with terrorists who want to strike us at any cost and who are extremely violent."
Hollande said: "Human rights are denied by fanatics, and France is clearly their target."
He announced that a state of national emergency - due to end on July 26 - would be extended by three months and that additional soldiers would be deployed for security.
French officials quickly concluded terrorism was the likely motive, as the scope of the slaughter grew clear. The use of a large commercial truck as the main weapon of death raised new questions about how to prevent such attacks.
There was no immediate claim of responsibility, and the identity of the driver was not immediately clear, but the Nice-Matin newspaper reported that he was a 31-year-old Frenchman of Tunisian origin. He was killed in a shootout with police.
This week Patrick Calvar, the head of domestic intelligence in France, had warned that "the greatest threat" was from people who trained and fought in Syria and Iraq, like those who carried out November's attacks in Paris that left 130 dead. And now for the third time in 18 months, a deadly terror attack has happened in the country.
Nice has rarely felt like a place of fear. Many leading artists have made their homes there. Henri Matisse, who helped define the city with fanciful, brightly coloured paintings, arrived in 1917 and sat out World War II there.
But nothing quite matches the grandeur of the Promenade des Anglais, literally the walkway of the English. The name comes from the substantial number of English aristocratic families that, in the second half of the 18th century, would travel there to spend winters.
It was so familiar that one of Agatha Christie's mysteries takes place on a luxury train used primarily by British travellers destined for Nice and the French Riviera.
But from now on, the name of the promenade will evoke different images: The spacious lobby of the 103-year-old luxury hotel Negresco turned into a makeshift hospital ward. A covered body in the street with a child's doll lying alongside.
Damien Allemand, a reporter for Nice-Matin, said he "saw bodies flying like bowling pins" as the vehicle raced forward.
"Heard sounds, howls that I will never forget," he wrote.
He ran away with other crying, screaming people, then returned to the promenade where he encountered a sobbing man.
"The dead are everywhere," the man told Allemand. "He was right," the reporter wrote. "Just behind him, lifeless bodies every five metres, limbs ... blood."
The world reacts
President Barack Obama condemned what he said "appears to be a horrific terrorist attack" in Nice. "Our thoughts and prayers are with the families and other loved-ones of those killed." Secretary of State John Kerry called it a "horrendous attack in Nice". Both presidential candidates also condemned the attacks, Republican Donald Trump declaring "this is war" and Democrat Hillary Clinton vowing "we will not be intimidated".
Russian President Vladimir Putin says he has been "shocked by the violence and exceptional cynicism" of the attack. Although the cause of the attack has not been officially confirmed, Putin said in a message of condolences to French President Francois Hollande that terrorism can be defeated only if "all civilised mankind pulls efforts together" to fight militants, their leaders as well as targeting their financial backers "wherever they are hiding".
European Council President Donald Tusk yesterday expressed consternation that France was attacked on its national day and said the world stands united with the French people. "It is a tragic paradox that the victims of the attack people celebrating liberty, quality and fraternity. We will stand united with the families of victims, the French people and the Government in the fight against violence and hatred," he said.
Premier Li Keqiang said "we strongly condemn terrorism of all forms. We express our condolences to the victims and we will fight all kinds of terrorism".
Foreign Minister Didier Reynders expressed dismay that France was once again the target of an apparent terrorist attack. "We condemn such an attack, maybe a terrorist attack, but such an attack in France again."
Foreign Minister Mevlut Cavusoglu said: "We strongly condemn and damn the terrible terror attack that occurred in the French city of Nice. We deeply share the pain of the French people. Turkey is in full solidarity with France in the fight against terrorism. We will continue our struggle against these baseless [people] with determination. First and foremost, terrorism is the rape of humanity and universal values."
Foreign Minister Julie Bishop said three Australians suffered minor injuries while fleeing the scene. "It has shocked France, it has rocked it to its core," Bishop said. "This should have been a time of great national pride and celebration." Bishop condemned the violence, saying it was a reminder that "no country is immune from terrorist attacks". "We support our friends and partners in France and we join with others around the world in hoping that this will be the end of this type of horrific incident that is targeted at unarmed civilians," she said.
United Arab Emirates
The seven sheikhdoms of the United Arab Emirates condemned the "heinous terrorist crime" that struck Nice. In a statement on the state-run WAM news agency, Emirati Foreign Minister Sheikh Abdullah bin Zayed Al Nahyan pledged to stand with the people of France. Sheikh Abdullah also stressed the attack "makes it imperative for everyone to work together decisively and without hesitation to counter terrorism in all its forms". The UAE is part of the US-led coalition targeting the Isis and hosts American and Western military personnel involved in the fight.
- Washington Post, Agencies