Nice - At least 80 people have been killed after a truck slammed into a crowd of people celebrating Bastille Day in the southern French city of Nice.Here is what we know about what French President Francois Hollande has declared an "undeniable" terrorist attack.How did the attack unfold? The white 19-tonne truck plunged into the crowd at around 23:00 (21:00 GMT) on Thursday night as hundreds of people were on Nice's beachfront Promenade des Anglais to watch the fireworks for France's national day.Christian Estrosi, head of the local region, said the driver had fired a pistol several times before being shot dead by police.A source close to the investigation said an "inactive" grenade was found inside the vehicle, as well as "several fake rifles".Interior Minister Bernard Cazeneuve told reporters 80 people had been killed after the truck ploughed 2km through the crowd, who had just finished watching the firework show.As rumours swirled online, interior ministry spokesperson Pierre-Henry Brandet dismissed reports that people had been taken hostage.The attacker is yet to be named, but the identity papers of a 31-year-old French-Tunisian were found in the truck, according to a police source. The papers indicate the man is a Nice resident.Was this a jihadist attack?The attack has not been claimed by any group, but Hollande said in an address to the nation early Friday that the attack was of an "undeniable terrorist nature".Prosecutors say the probe will be handled by anti-terrorism investigators."Investigations are currently underway to establish if the individual acted alone or if he had accomplices who might have fled," interior ministry spokesperson Brandet said.The attack comes with France under a state of emergency following the Islamic State attacks in Paris in November that left 130 people dead.How has the government reacted?Hollande announced that the state of emergency would be extended by three months and army reservists called up to boost security.He also said France would strengthen its role in Iraq and Syria, where it is part of the international coalition fighting ISIS jihadists.He will chair a meeting of top military and security officials later on Friday to decide on possible further steps.Has anything like this happened in France before?In December 2014, two men ploughed their vehicles into pedestrians in two days - separate incidents that left France reeling.The first driver shouted "Allahu Akbar" (God is greatest) as he drove into people in the eastern city of Dijon, injuring 13.The 40-year-old had a long history of mental illness, and no ties to jihadist groups, the government said.A day later, a man rammed a white van into a Christmas market in the western city of Nantes, killing one person and injuring nine others. He then stabbed himself several times.Prosecutors said a notebook was found in his vehicle in which he spoke of his "hatred for society" and said he feared "being killed by secret agents".The man committed suicide in his prison cell in 2016 while awaiting trial.Who are the victims?A local hospital official said that at least two children were among the dead and around 50 had been admitted to hospital, some of whom were fighting for their lives.Two of the dead were American citizens, a state department spokesperson said.