The monster behind the wheel of a box truck that plowed into Bastille Day revelers in Nice late Thursday - killing at least 84 - was a creepy Tunisian loner sometimes prone to violence, but not seen by police or neighbors as a religious fanatic, according to French reports.
Bouhlel reportedly rented the truck earlier this week.
Police identified the attacker as Mohamed Lahouaiej Bouhlel, a 31- year-old Nice resident, and said he had drawn a gun on them. French media said ID papers belonging to a French-Tunisian were found in the truck.
"They had to stay there for a couple of hours, but people wouldn't even come out - they were so frightened - until the police came and said it was OK to come out", he said. After the attack, they found a handgun, rifle and a number of fake weapons and grenades in the truck.
The massacre again prompted questions as to why France is such a persistent target for such attacks and what can be done to prevent such a unsophisticated assault.
Hollande, flanked by prime minister Manuel Valls and health minister Marisol Touraine, said numerous 84 dead included foreigners as well as children.
"I don't have words", said one festival-goer.
Hollande said France would observe three days of national mourning from Saturday, Paris city hall said the Eiffel Tower will be lit in France's national colours on Friday in tribute to the victims.
France has lived with soldiers in the streets since the November attacks, and much of the country was under intense security during the month-long European football championships, which ended July 10 without incident.
In France, there were two other recent attacks using vehicles, but it was disputed whether the assailants had links to terrorist cells.
Neighbors in the residential neighborhood in northern Nice where Bouhlel lived described him as a handsome man but an unsettling presence.
"He kept to himself but would always rant about his wife", she said. The driver, who was carrying a firearm, was subsequently shot and killed by police outside a hotel and casino.
He had hired the truck on Monday. Photographs after the carnage showed its front badly damaged and riddled with bullet holes. Of the injured, about 50 are children. Some were "hanging between life and death".
"There are many children", Hollande said.
- ARMENIA: An Armenian citizen was also among the dead, the foreign ministry said.
The region's interim mayor and police and crime commissioner Tony Lloyd said: "Our thoughts remain with the people of Nice following last night's devastating attack".
"I stood on the balcony, right on the promenade and saw how people celebrated there, and how suddenly a truck drove through the crowd", Richard Gutjahr, 42, who shot smartphone video footage of the rampage, told AFP on Friday.
In a Facebook video, witness Tarubi Wahid Mosta recounted the horror on the promenade.
"Within a few seconds it was nearly upon me", Coates told the BBC. "It looked like a battlefield", he said.
President Barack Obama condemned the attack and, noting it occurred on Bastille Day, praised "the extraordinary resilience and democratic values that have made France an inspiration to the entire world".
France is a major part of a U.S.-led mission conducting air strikes and special forces operations against Islamic State in Iraq and Syria, and has also sent troops to West Africa to battle Islamist insurgents there.