He was named as the driver after police found an identification card, possibly a driver's licence, in the cab of the delivery truck used in the attack. Another 55 people were still being treated, including several who were fighting for their lives.
A 68-year-old neighbor who declined to be identified beyond his first name, Mohamed, said he had seen the suspected assailant in the apartment complex and believed that he had a wife and three children.
Middle East states and leading Muslim clerics united in condemning the attack calling for a joint struggle against extremism.
Police killed the driver "apparently after an exchange of gunfire, " Eric Ciotti, the ranking politician of the Alpes-Maritime department that includes Nice, told BFM television.
The motivations and affiliations, if any, of the attacker are still unclear. There was no sign of any other attack.
The Nice terror attack has been particularly hard because of the amount of children impacted. In November, 130 were killed and 368 injured in a series of coordinated terrorist attacks in Paris.
Over the past week, France had been breathing a sigh of relief after successfully hosting the month-long Euro 2016 football championship, which passed off without incident despite fears of attacks. Stay at home for the time being.
But the terror attack wasn't far from people's minds here, including Pierre who says many people at the Roundhouse Community centre were determined to have a good time.
"A fraction of a second later, an enormous white truck came along at a insane speed, turning the wheel to mow down the maximum number of people", he said.
Damien Allemand, the paper's correspondent, was quoted as saying: "People are running. The vehicle accelerated and ran in a very odd way right in the middle of the crowd", he said. There are people covered in blood. "There must be many injured".
Social media carried images of people lying apparently lifeless in pools of blood.
He also said France would strengthen its role in Iraq and Syria, where it is part of the global coalition fighting IS jihadists. "Though I have never been to Nice, my friends have told me that it is a wonderful city with nice people", Dmitry said. "There was carnage on the road", a witness told the AP".
In a national address in the early hours of the morning, Hollande said that it was without doubt a terror attack.
Hollande also called up army reservists to bolster security services that are stretched to the limit.