(Photo Credit: Johannes Eisele/AFP/Getty Images)

A U.S political science professor teaching in Afghanistan, a Chicago woman and a Somali-American nutrition specialist were among the 21 people who died in a Taliban attack against a popular Kabul restaurant.

The American University of Afghanistan has confirmed that Alexandros Petersen, a professor of political science there, died in the Saturday assault. Petersen, who had just arrived in Kabul, has family in Washington, university president Michael Smith said.

"I liked him tremendously, he was a very giving person and also very intelligent," Smith said. "He would have been a fantastic professor for us. It's such a tragedy to have people so early in their lives lose the opportunity to contribute in the way they wanted to contribute.

"Today on campus I was hearing how terribly sorry and devastated they are because of the loses endured," said Smith.

Alexis Kamerman, a Chicago native and student development specialist who also worked for the American University of Afghanistan, was one of the three Americans who died in the attack, according to ABC News station WLS-TV in Chicago and the Sun-Times.

The third U.S. victim was UNICEF nutrition specialist Basra Hassan, a Somali-American, according to the United Nations.