Bastille Day attack: What we know so far

(CNN) A truck rammed into a crowd that had gathered to celebrate Bastille Day in NiceThursday, killing at least 84 people, according to French media.

The crowd had watched a fireworks show on the promenade and was leaving the area when a large white truck appeared. The driver of the truck fired a gun at people and then plowed through the crowd on the main street for more than a mile. One witness said that the truck appeared to zigzag through the crowd, and another witness said the driver appeared to accelerate when hitting people. The driver was shot and killed by police.

Here's the rundown:

Who's responsible? The driver of the truck has been identified by the French government and anti-terrorism officials as Mohamad Lahouaiej Bouhel, a 31-year-old French-Tunisian and a resident of Nice. No group has claimed responsibility. But the presidents of France and the United States are calling this a terror attack.

French president delivers yet another somber address: French President François Hollande vowed to crack down on France's enemies and is asking parliament to extend the country's state of emergency by three months. "France is afflicted, but she is strong, and she will always be stronger than the fanatics who want to strike her today," he said.

What was the scene like? One minute, it was a jubilant celebration of Bastille Day. The next, it devolved into chaos and carnage.

World leaders express shock and sympathy: It feels almost routine now. Another terror attack results in an outpouring of condemnation against the attacker and expressions of solidarity for the victims.

Have trucks been used as weapons before? Yes, they have been used as weapons before, but the lethality of such attacks had been relatively low until the attack in Nice. Not only do we have to worry about truck bombs, now the vehicles are used as weapons, writes Peter Bergen, CNN's national security analyst.

What's the reaction in the U.S.? Presidential candidates Donald Trump and Hillary Clinton chimed in on the France terror attack. "We have to be tough," Trump said, reiterating that the United States should reverse its decision to allow Syrian refugees into the country. Clinton told CNN that greater intelligence gathering, not military force, is necessary. Former House Speaker Newt Gingrich wants the United States to test and deport every person with a Muslim background who believes in Sharia law.