"It Was Horror": At Least 84 Dead in Bastille Day Attack in France

France-video grab taken Thursday July 14, 2016-AP-ONE TIME USE-H 2016

Paris has opened a terrorism investigation after a truck plowed into a crowd of revelers celebrating Bastille Day in Nice on Thursday night.

A truck slammed into a crowd celebrating Bastille Day on the waterfront in Nice, France, killing 84 and injuring up to 100 others.

Christian Estrosi, the president of the region that includes Nice, says the truck, which plowed through over a mile of revelers, was loaded with arms and grenades. The driver was killed by police in what appeared to be a subsequent gun battle and the Paris prosecutor's office has opened an investigation for "murder, attempted murder in an organized group linked to a terrorist enterprise."

Estrosi told French news network BFM TV that "the driver fired on the crowd, according to the police who killed him," adding the truck was driven by someone who appeared to have "completely premeditated behavior." 

The probe is being handled by France's intelligence agency and judicial police.

On Thursday night amid celebrations of the national holiday in the French resort city, the truck drove onto the sidewalk and began to zig-zag. Video footage showed men and women — one or two pushing strollers — racing to get away from the scene. Photos showed the truck with at least half a dozen bullet holes punched through its windshield.

Estrosi tweeted late Thursday, "This is the worst tragedy in the history of Nice." At the time, 70 victims had been reported.

He followed that tweet with another, saying, "We are terrified and we want to extend our sincere condolences to all the families. #Nice06"

Pierre-Henry Brandet told BFM TV of the climbing numbers: "It's going to be a very high toll."

It was not immediately clear who would have been behind an attack, but France has recently seen a spate of dramatic assaults by jihadists, including the Islamic State.

Late Thursday, President Obama condemned the "horrific" attack while offering U.S. assistance in investigation.

Presumptive GOP nominee Donald Trump was due to reveal his vice presidential pick on Friday but has postponed the announcement due to the tragedy.

"In light of the horrible attack in Nice, France, I have postponed tomorrow's news conference concerning my Vice Presidential announcement.," the businessman-turned-politician tweeted Thursday afternoon.

Sky News' Mark Stone said on Sky News Live that the imagery of the scene in Nice was too horrific to show. Adding, "There are people dead all along the street."

He quoted Nice prosecutor Jean-Michel Prette as shooting down circulating reports of a hostage situation.

Sylvie Toffin, a press officer with the local prefecture, said that the truck "hit several people on a long trip" down the sidewalk near Nice's Palais de la Mediterranee, a building that fronts the beach. Wassim Bouhlel, a Nice native who spoke to the AP nearby, said that he saw a truck drive into the crowd.

Eric Ciotti said on France Info radio that, "It's a scene of horror," with bodies strewn along the roadway. 

"There was carnage on the road," Bouhlel said. "Bodies everywhere."

Images circulating on social media showed grisly scenes of piles of bodies in the street. 

Nice Matin journalist Damien Allemand, who was at the waterside, said the fireworks display had finished and the crowd had got up to leave when they heard a noise and cries.

"A fraction of a second later, an enormous white truck came along at a crazy speed, turning the wheel to mow down the maximum number of people," he said.

"I saw bodies flying like bowling pins along its route. Heard noises, cries that I will never forget."

Allemand said people took shelter in a nearby restaurant, where he continued to hear people shouting for missing family members. He ventured out and saw bodies, blood and body parts all along the road.

"This evening, it was horror," Allemand concluded.

European Council president Donald Tusk says it is a "tragic paradox" that the victims of the attack in Nice were celebrating "liberty, equality and fraternity" — France's motto — on the country's national day.

Later, Estrosi announced on Twitter that the city's jazz festival, due to open on Saturday, and a Rihanna concert planned for Friday evening, have both been canceled after the deadly attack.

The singer was in Nice during the attack, but her rep confirmed to Billboard that "she's safe."

Flags will be lowered across the city on Friday.