He is Fouad Mohamed-Aggad, CNN affiliates BFMTV and France 2 reported. He, like the other attackers, blew himself up.
The 23-year-old man is from a small town near Strasbourg who traveled to Syria in 2013, the stations said.
The official said Mostefai entered Turkey in 2013 and there is no record of him leaving the country.
On 10 October 2014, Turkey received an information request regarding four terror suspects from the French authorities, but Mostefai was not among them.