GAINSEVILLE, Fla.

It was supposed to be celebration time.

But a graduation ceremony last Saturday at the University of Florida became tainted with a depressing display of racism instead.

It happened when graduating students, many of them African-American, began dancing and enjoying their moment on stage in cap and gown and then found themselves forcibly pushed off the stage by a white faculty member who apparently found their open show of happiness too much to bear.

In a video that has gone viral, the still unidentified faculty member in full academic regalia can be seen grabbing graduates as they break into a dance after their names are called to cross the stage and collect their diplomas.

Students later said the college usher grabbed them and forced them away as they followed the longtime tradition of performing a “stroll” across the stage, a 5- to 10-second version of their fraternity’s or sorority’s steps or, in one case, a backflip.

Oliver Telusma, 21, who earned a degree in political science with an eye toward going to law school, said he was one of the graduates who was manhandled when he started to dance on stage.

“I had just started … and he picked me up and turned me around, which I thought was kind of embarrassing and degrading to be handled in that manner,” Mr. Telusma said.

“This little snapshot of what happened at graduation is a little bit of insight into how the university treats minority students, especially black students,” one student said.

Other videos show the usher also manhandled a few white students who paused to wave to relatives. In a separate video, the usher can be seen hustling off stage a white graduate who stopped to take a selfie.

However, students who were present claimed the usher saved his most vigorous action for the African-American students who broke into a dance.

The video has created outrage among parents and alumni, as well as others who watched the video via social media.

One Twitter-user wrote: “Every time a Black student took more than TWO seconds, he aggressively pushed them.”

An alumna wrote that she is “completely disgraced at the treatment of these students who earned their spot on that stage.”

University of Florida President Kent Fuchs, who kept mum on the stage as the usher humiliated the celebratory degree-winners and offered no response the rest of the day, finally went on Twitter early Sunday with his first reaction on behalf of the school.

“During one of this weekend’s commencement ceremonies, we were inappropriately aggressive in rushing students across the stage. I personally apologize and am reaching out to the students involved,” Dr. Fuchs wrote in seeking to quell the uproar and the embarrassing national attention his school’s commencement secured.

“The practice (of grabbing students on stage) has been halted for all future ceremonies, and we will work to make sure all graduating students know we are proud of their achievements and celebrate with them at their graduation.”

The university later issued a statement that an investigation has begun against the faculty member who was responsible, promising appropriate, though unspecified, action.

Todd Simmons, a 1985 graduate who is now an associate vice chancellor at North Carolina A&T State University, expressed the sentiments of many in his response to President Fuchs’ Twitter statement.

“I appreciate your candor,” Dr. Simmons wrote. “I also respectfully suggest an inquiry is in order regarding how such a ‘practice’ came to be approved & carried out in the 1st place, w/ what appears to be clear racial differences, in front of thousands. The vids (sic) are disturbing.”