The man responsible for turning a night of celebration into one of carnage in the seaside city of Nice was a petty criminal who had not been on the radar of French intelligence services before the attack.
The Islamic State group claimed Mohamed Lahouaiej-Bouhlel as a "soldier" today, but what is known so far about Bouhlel suggests a troubled, angry man with little interest in Islam.
However, the French interior minister said today the truck attacker was likely ''radicalised very fast''.
French Prime Minister Manuel Valls had also said on Friday that the man behind the Nice truck attack was a "terrorist" who was probably linked to radical Islam.
"He's a terrorist who is probably linked to radical Islam in one way or another," Valls told French television the day after 84 were killed at a Bastille Day fireworks display in the French Riviera city.
The thirty-one-year-old was born in Msaken, a town in Tunisia, but moved to France years ago and was living in the country legally, working as a delivery driver.
At an apartment block in the Quartier des Abattoirs, on the outskirts of Nice, neighbours described the father of three as a volatile man, prone to drinking and womanising, and in the process of divorcing his wife.
His father said Bouhlel had violent episodes during which "he broke everything he found around him."
"Each time he had a crisis we took him to the doctor who gave him medication," Mohamed Mondher Lahouaiej-Bouhlel told BFM television.
His son had not visited Tunisia in four years and had not stayed in contact with his family, he said.
"What I know is that he didn't pray, he didn't go to the mosque, he had no ties to religion," said the father, noting that Bouhlel did not respect the Islamic fasting rituals during the month of Ramzan.
In a news conference yesterday, hours after the attack in which 84 were killed and 202 were wounded, prosecutors said they had found no links to the Islamic State extremist group.
Bouhlel had a series of run-ins with the law for threatening behavior, violence and theft over the past six years. In March, he was given a six-month suspended sentence by a Nice court for a road-rage incident.
His court-appointed lawyer, Corentin Delobel, said he observed "no radicalisation whatsoever," and Paris prosecutor Francois Molins said Bouhlel was never placed on a watch list for radicals.
Records show that the 19-metric-ton truck that was rammed through the seaside crowd in Nice was rented in the outskirts of the city on July 11 and was overdue on the night of the attack.
About 25 minutes before the July 14 fireworks show, a popular event that draws hundreds of thousands of people to the Nice seafront each year, Bouhlel climbed into the vehicle and drove toward the city centre.
Shortly after 10.30 pm, he drove onto the Promenade des Anglais that had been closed to traffic for the night.
Witnesses described seeing how Bouhlel purposely steered the truck to hit men, women and children as they tried to flee.
"It was such a nice atmosphere before this started," recalled Sanchia Lambert, a tourist from Sweden who had come to visit family in Nice.
Her husband, John Lambert, said the couple was almost struck by Bouhlel. "I saw his face," Lambert told The Associated Press. "He was totally focused."