The missing student has been identified as Nick Leslie. According to his Facebook page, the 20-year-old was originally from Italy but grew up in Del Mar.
He was on the promenade when the truck barreled through crowds of people celebrating Bastille Day, killing 84 and injuring dozens more.
ABC7 News spoke with Leslie's father, who says other students with his son's study abroad program are currently looking all over Nice for him. He adds that the U.S. Embassy is helping out and UC Berkeley has mobilized.
Leslie's father says the family's hearts and prayers are with the people in Nice and with all the victims of the terror attack.
On Friday, the university released a statement saying Leslie is one of 85 students attending the study abroad program in France.
PHOTOS: Truck drives through Bastille Day crowds in France, killing scores
Of the three injured, UC Berkeley says two sustained broken legs and are being treated in the hospital, and a third had a broken foot.
All of the students were attending a 15-day program called Entrepreneurship and Innovation in Europe, part of the international European Innovation Academy.
According to the university, "The program has been suspended temporarily to commemorate a national three days of mourning in France, and will continue through its planned end date on July 24. The campus has offered to bring home any students who wish to leave the program before its end date, and so far, three students have chosen to do so and return home to the U.S."
Click here to read the full statement from UC Berkeley.
ABC7 News reporter Tiffany Wilson contributed to this report.