The following is a script from "Bastille Day Tragedy" which aired on July 17, 2016. Seth Doane is the correspondent. Nicole Young and Katie Kerbstat, producers.
The Bastille Day attack of this past Thursday in Nice, France, brought to reality a nightmare of police forces around the world: an attack on a large public holiday celebration. The man responsible was a Tunisian-born, French resident who drove a large truck straight into a crowd of thousands celebrating the French Independence Day on the seaside promenade. He was shot and killed by police, but not before he killed at least 84 people and injured at least 200 more. His father told reporters he had a history of violence and mental illness and investigators are working to determine if he was radicalized or at the very least inspired by ISIS to carry out the attack. Correspondent Seth Doane sent us this report from Nice.
There's not just one memorial to the victims in Nice, but dozens and dozens of them. They're carefully placed up and down the waterfront. Each one, a tribute to lives lost on the more than a mile-long stretch of road where that truck came careening through the crowd. Emotion is raw and for those who were there that night, it's not just what they saw.
Silvia Jordan: When he was running over bodies, you hear the noise, you know, the crack, just the sound of running over people. The screams...
Seth Doane: Coming to Nice for Bastille Day is sort of a family tradition?
Aliyah Jordan and her mom Silvia have been coming to Nice from North Carolina for more than a decade. On Thursday night, that truck came barreling toward them. Silvia Jordan's father, Gaetano Moscato, got caught underneath.
Silvia Jordan: I noticed that my dad -- his lower leg was gashed open -- the bone was sticking out -- everything was open.
Seth Doane: How is it to see something like this?
Aliyah Jordan: It's traumatic. It doesn't feel real. There's nothing you can do. You're just completely hopeless. You try and flag down ambulances and people are grabbing your hand and pulling you back and saying there is nothing you can do. People just cry. They hang on to their loved ones. There is nothing you can do.
Moscato lost his leg, but survived. This video, shot by an eyewitness, is too disturbing to show in its entirety but reveals the horror that unfolded that night.
Seth Doane: Was there enough security in place?
"I don't think so," Christian Estrosi told us.
Estrosi was Nice's mayor until a few weeks ago and now he's the president of the region. He told us France is "at war" with radical Islam and supports his government's view that the attacker, Mohamed Lahouaiej Bouhlel, committed a "terrorist act."
"I asked for the same security measures to be put in place for Bastille Day here as France had for the Euro-2016 sporting event," Estrosi told us, "unfortunately that wasn't the case."
Thirty-thousand people gathered along Nice's waterfront for the holiday and the packed promenade made a vulnerable target for Bouhlel's 21-ton truck going 55 miles-an-hour.
Seth Doane: You see the intelligence. Who was this man?
Christian Estrosi, translated: "We know he was arrested in January for violent acts. We're talking about a dangerous individual."
The attacker was 31 years old and lived alone in this neighborhood in Nice. He was estranged from his wife and kids and, though he was known to police as a petty criminal, he was not on any terrorist watch list.
Christian Estrosi believes Bouhlel was not acting alone and a terrorist attack in his city was exactly what he'd worried about.
Seth Doane: You were the mayor. You're an elected official. This happened on your watch.
"I'm not taking this well at all," he admitted and "I don't want any suffering like that in my country."
Bouhlel struck at the heart of Nice. French authorities say he took practice runs in his rental truck on this promenade, which runs along the water. And then after the attack, these hotels became make-shift hospitals. Their lobbies turned into trauma centers to deal with the flood of victims. Those who were still able helped as they could.
Laurent Laubry, a police officer, and his wife, Cecile Coine, a nurse, had been out celebrating and once they got their kids to safety, they rushed to work.
"In the moment, you just react...but", the nurse admitted to us, "today I went to see a counseling service and I broke down."
Seth Doane: You say you went to see a psychologist, why, what did you talk with the psychologist about?
"It's not human," Coine said. "What we saw is not human."
Silvia and Aliyah Jordan say it's too tough to look at photographs they'd taken of the family at the fireworks just before the tragedy -- just before everything changed.
Seth Doane: When you looked up and down that promenade? What did you see?
Aliyah Jordan: There was somebody on the rocks that was barely conscious. There were other people that were dead further down. There was a dead child next to us as well, and when the truck first passed -- someone, they picked up their child that was limp and just screamed and they said, "No."
Three days later, Nice is just beginning to grapple with this. Candles and flowers seem out of place in this Mediterranean paradise. Here blood still stains the streets under some of these tributes while painful memories are etched much deeper.