Search Continues For Missing American Student in Nice As ISIS Claims Responsibility For Attack | Inside Edition

Search Continues For Missing American Student in Nice As ISIS Claims Responsibility For Attack

Nicolas Leslie, 20, a junior studying at the University of California, Berkeley, is still missing, his school said Friday night.

The family of a Californian student who was in Nice at the time of Thursday's deadly attack is desperately searching for news of his whereabouts.

Nicolas Leslie, 20, a junior studying at the University of California, Berkeley, remains missing following the attacks that left 84 dead and hundreds more injured, the school said in a statement Friday evening.

Read: 21-Year-Old Student and Mom of 7 Among the Dead in Nice Truck Attack

The student, who is from Del Mar, was in Nice for a program at the European Innovation Agency, a non-profit school specializing in entrepreneurship, and attended Thursday night's Bastille Day fireworks with friends.

Nick Leslie is a junior at Berkeley. (Facebook)

Leslie's father, Conrad, told The Wall Street Journal his son is believed to have sidestepped the truck as it barreled along the promenade, plowing down families as they celebrated France's national holiday. 

"We think he escaped the truck, but he could have been trampled," he said. "Our real frustration is how long it has taken to develop a list [of the injured]. It seems like something you would do immediately."

The university said in a statement Friday that Leslie "is the subject of an extensive search by university staff, local officials and family." A representative of their study abroad program has also flown to France to assist.

Read: Family Reunited With Baby Boy Lost in Chaos of Nice Attack

Three other Berkeley students were injured in the attack. Vladyslav Kostiuk, 23, a senior computer science major, suffered a broken leg while 20-year-old Diane Huang, a senior majoring in environmental economics and policy, sustained a broken foot. Both have since been released from hospital and are now back in their dorms in Nice, the university said Friday evening.

On Friday, Kostiuk shared an image of his injuries on Facebook.

"I would say only one thing: I was lucky, I'm alive, unlike other people that were walking with me," he wrote.

Huang also shared a message on Facebook, asking for information on Leslie. "Please... help us find our friend," she wrote.

A third student, 21-year-old sophomore Daryus Medora, remains in hospital with a broken leg, according to the university.

Two Americans were also killed in the attack. Sean Copeland, 51, and his son Brodie, from the Austin, Texas area, were on vacation with family when they were mowed down by the driver, Mohamed Bouhlel.

Sean and Brodie Copeland were killed in the attack Thursday night. (Facebook)

On Saturday, ISIS claimed responsibility for the attack, calling the killer, a 31-year-old Tunisian-born Frenchman, a "soldier."

The Aamaq news agency cited a "security source" as saying the attacker "carried out the operation in response to calls to target the citizens of coalition countries fighting the Islamic State."

The statement implies that the man acted independently and there is no evidence IS was involved in planning the attack, the AP reported.

French authorities said Friday that the killer had not been on the radar of French Intelligence.

Watch: The Most Heartbreaking Scene From Aftermath of Nice Attack