NORMAN, Okla. (AP) — Almost a generation ago, the University of Oklahoma set out to raise its profile, seeking to build a regional school that served mostly students from the Southwest into a leading institution that attracted top scholars.

President David Boren made striking progress, achieving a reputation that now extends well beyond the Sooners football team that once defined the campus. But those improvements seem in peril after members of a fraternity were caught on video chanting a racial slur. The chant referenced lynching and indicated black students would never be admitted to OU's chapter of Sigma Alpha Epsilon.

Boren, a former Oklahoma governor and U.S. senator, acted swiftly. He immediately severed ties with the fraternity and ordered members to vacate their house. On Tuesday, he expelled the two students who appeared to be leading the chant for creating a hostile educational environment and promised others involved would face discipline.

"I have emphasized that there is zero tolerance for this kind of threatening racist behavior at the University of Oklahoma," Boren said in a statement.

Since taking the helm of the state's flagship university more than 20 years ago, Boren has made ambitious efforts to recruit top students and faculty.

The school offers generous scholarships to all National Merit scholars and enrolls more of them than any other public university in the nation. It has produced 29 Rhodes scholars.

Boren also expanded the honors program and raised large amounts of money for endowed chairs — so much that the state had to scale back an offer to match the donations.

The video was taken on a bus going to a Founder's Day event at a country club. The person who recorded it has cooperated with the investigation, Boren said Tuesday ahead of a Board of Regents meeting.

Also Tuesday, one fraternity member seen on the video and parents of another issued statements apologizing.

In a statement emailed by his father, Parker Rice said the incident "likely was fueled by alcohol," but "that's not an excuse." He said he was "deeply sorry" for the performance, calling it "wrong and reckless," ''a horrible mistake" and "a devastating lesson" for which he is "seeking guidance."

He said he withdrew from the university Monday and that threatening calls to his family prompted them to leave their North Dallas home.

The parents of Levi Pettit posted a statement online saying they were shocked by their son's actions, that he "made a horrible mistake, and will live with the consequences forever."

Also on Tuesday, Beauton Gilbow, the fraternity's house mother, issued a statement that addressed a video from 2013 showing her repeating a racial slur against blacks as music plays in the background. Gilbow said she was singing along to a song. She said she was "heartbroken" by the portrayal that she was racist but understood how the video must appear in the context of the week's events.

A "house mom" is a housing director who might oversee staff and finances at a sorority or fraternity house.

Some students at OU, particularly African-Americans who make up about 5 percent of the campus population, said racism is alive and well and that a mostly segregated fraternity and sorority system is at least partially to blame for creating an environment where racism can thrive.

"It's too segregated," said Markeshia Lyon, a junior from Oklahoma City who is black. "That's something that's passed down, and that's something that needs to change."

Lyon recalled trying to attend a fraternity party her freshman year with several friends, all of whom were African-American, and being told they were not welcome.

"It was very hurtful," she said. "I would never set foot on that street again."

But fraternity members say chapters at Oklahoma have taken steps to diversify, recruiting more African-American, Asian and Hispanic students.

"We've always fostered a community where anyone who is qualified can enter. We don't look at your race," said Jordan Bell, an African-American senior from Washington, D.C., who joined a mostly white fraternity. He said more than 10 percent of the roughly 100 members of his Phi Kappa Psi fraternity now are African-American.

Bell said some fraternities and sororities are more diverse than others, and Boren acknowledged at a news conference Monday that more needs to be done to attract minority students to the university and the fraternity-sorority system.

"Some are doing quite well. They're making progress," Boren said. "Others are still locked in the past, and they need to realize that it enriches the experience and the friendships that are involved if they become more diverse as organizations.

"I don't think we can paint the whole Greek system with a broad brush."

The university has succeeded in breaking down some racial barriers, mainly through its athletics programs, which is why the video reopens old wounds.

Running back Prentice Gautt, for example, became the first black football player at the school in the late 1950s, long before many universities had integrated collegiate athletics. Yet today, members of the school's predominantly black football and basketball programs play before overwhelmingly white crowds.

While the school made strides on the playing field, it seemed to be losing ground elsewhere. The enrollment of black students declined. Ten years ago, roughly 6 percent of students at the Norman campus were black, according to university statistics. Last year, the figure hovered just above 5 percent.

The video also revived painful memories of the state's history of racial violence.

In 1921, a race riot in Tulsa left some 300 blacks dead and an entire section of town in economic turmoil — scars that remain today in the state's second-largest city.

Only two years ago, the Tulsa City Council voted to rename the city's glitzy arts district, which had been named after Wyatt Tate Brady, the son of a Confederate veteran and Ku Klux Klan member. But the change was vehemently opposed by some locals.

An entire swath of southeastern Oklahoma is still called Little Dixie today.

JeffriAnne Wilder, associate professor of sociology at the University of North Florida in Jacksonville — where a school board decided in 2013 to rename a high school named after an honorary Ku Klux Klan leader — said the incident at OU is a quick reminder of how far the state, and the U.S., has to go in dealing with racial issues.

"It's saddening and unfortunate that just a few days ago, we were commemorating Selma," Wilder said, referring to the 1965 civil rights march in Alabama from Selma to Montgomery. "We have to pause and on one hand, we can look back and see how far we've gone and on the other hand, how far we have to go."

"The millennial generation," she added, "is supposed to be both colorblind and post-racial, but that's not true."

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Juozapavicius reported from Tulsa.

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Follow Sean Murphy at www.twitter.com/apseanmurphy and Justin Juozapavicius at www.twitter.com/juozapa .