The University of Florida is being criticized after an usher manhandled several black students during a graduation ceremony on Saturday. The white usher pushed and grabbed students attempting to stroll—a dance significant to black fraternities—dance, and celebrate while crossing the stage.

In videos of the ceremony posted to social media, the man can be seen grabbing and yanking at students after they recieve their diploma.

Of the 5,000 students who participated in the ceremony on Saturday, spectators say the usher's behavior seemed to exclusively target black students. "It was definitely contingent on your race," graduate Nafeesah Attah told Good Morning America. “Other white students who were dancing were not perceived as a threat.”

University of Florida president W. Kent Fuchs apologized for the incident. “I personally apologize, and am reaching out to the students involved,” he tweeted.

Meanwhile, the usher in question remains unidentified.