So far 84 people had been killed and many others critically ill in hospital in an outrage being blamed on Islamic State.
The streets and beaches had been full of people celebrating France's national holiday.
The truck tore along the pavement near Nice's Palais de la Mediterranee, mowing victims down at speed.
"We were on the beach when it happened - at the most we were 300 metres from the attack," Laura told the Belfast Telegraph last night as panic gripped the Riviera city.
"There were thousands of families at the beach to watch the Bastille Day fireworks.
"The firework display had just ended and families had just started setting off their own on the shore.
"You could hear the sirens in the background, but I thought it was French police being overcautious - we had noticed a tense atmosphere on the lead-up to and during the Euro 2016 final.
"The sight of hundreds running towards us... I couldn't help but think of Tunisia," added Laura, referring to the beach attack in Sousse in which 38 tourists died. It is also just eight months since Islamic State terrorists killed 130 people in Paris.
Eyewitnesses said a gunman got out of the lorry and fired into the crowd. News agency reports said gunshots were heard, and the lorry windscreen was photographed riddled with bullets by French security forces.
Police shot the gunman dead, but an accomplice is believed to have fled the scene, and weapons and grenades were found in the lorry, according to reports.
Laura said that terrorism was on everyone's lips as panic spread.
"Hundreds of people ran along the beach not knowing what had happened - but all muttering ISIS," she said.
"A young couple told us a man went into the crowd with a Kalashnikov and killed lots of people.
"We didn't believe it, and walked into the old town.
"Walking through the quiet, narrow streets, I felt like I had escaped the madness of the beach, but suddenly there was lots of screaming and people running through the old town. It seemed the news had just hit them."
Footage on social media showed crowds fleeing in panic.
The president of the Nice region, Eric Ciotti, was last night at the scene, where bodies were strewn along the road.
"It's a scene of horror," he said.
Local man Wassim Bouhel said he saw the truck drive into the crowd and then witnessed a man emerge with a gun and start shooting.
"There was carnage on the road," Bouhel said. "Bodies everywhere."
Another eyewitness told reporters: "We saw a white lorry which drove directly into people on the Promenade des Anglais. A gunman fired into the crowd before being shot by police."
While no one had claimed responsibility, the SITE Intel Group tweeted last night that "pro-ISIS groups" were celebrating.
A French reporter described seeing a white van driving at high speed onto the famed Promenade des Anglais as people were leaving after the annual Bastille Day celebration display.
"We saw people hit and bits of debris flying around," the reporter said, adding that the incident took place near the city's famed Hotel Negresco.
"Terrified pedestrians screamed as they fled the area. "It was absolute chaos.
Another eyewitness, Ellen Savin, tweeted: "Apparently, shots were fired by police to stop the truck. People jumped into the sea in fear."
A huge security cordon was established, closing off the city's central Place Massena.
It was also feared last night that gunmen were holding hostages in the Meridien Hotel, the Hotel Negresco and the Buffalo Grill restaurant. Security forces and ambulances raced to the scene, and authorities from the local Alpes-Maritimes prefecture urged residents to stay indoors.
Yesterday was a public holiday, celebrating the anniversary of the storming of Paris's Bastille prison in 1789 and the start of the French Revolution.