DENVER -- A Colorado high school cheerleading coach was fired Friday after videos surfaced showing him pushing cheerleaders down in splits.

Denver Public Schools Superintendent Tom Boasberg said Ozell Williams was dismissed from his job at East High School.

"I have watched all of the videos," Boasberg said Friday. "As a superintendent, and as a father, and as an athlete, they are deeply disturbing. What happened was wrong."

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The videos show eight cheerleaders repeatedly being pushed into splits while their arms are held up by teammates. In one video, a girl appears to cry out in pain and repeatedly asks her coach to "please stop."

The videos were broadcast on KUSA-TV this week. The TV station says the videos were shot on the phones of two team members and were sent anonymously to the station.

Police have opened a child abuse investigation, and four other district employees have been placed on leave: the East High School principal, an assistant principal, an assistant cheer coach and a district lawyer.

Boasberg said East High administrators saw at least one of the videos in June and should have told police about it then. He said the principal and an assistant principal met with Williams after seeing the video and believed they had addressed the issue.

Boasberg said he didn't learn of the incident until this week. He said the district has hired a law firm to investigate how officials at the school and the district level handled the incident.

Williams couldn't be located for comment but told The Denver Post on Thursday the videos were taken out of context.

"You can definitely say that what was in the video could be seen in a different light," he told the newspaper. "I would love to tell my story, but I can't say anything else at this time."

Williams worked in multiple gyms throughout the Denver metro area. Most recently, he worked at Reunion Recreation Center, as a tumbling coachfor children, CBS Denver reports. Rec center management told CBS Denver that as of Thursday, Williams is no longer employed there.

Williams, the founder of a Denver-area tumbling school, was fired from Boulder High School in Boulder, Colorado, last year because of concerns about his techniques.

Boasberg said Friday that Denver Public Schools officials were unaware that Williams had worked with the Boulder school and that Williams had not told them about it.

Williams had worked as a contract employee with cheerleaders at Boulder High during two stints in 2015 and 2016 to help them with choreography and tumbling. He worked with the cheerleaders once or twice a week in the fall of 2015 and also during a summer camp in 2016.

He was dismissed three days into the four-day camp after a coach saw him using a technique similar to that seen in the Denver videos, said Randy Barber, a spokesman for the Boulder Valley School District, which includes Boulder High.

Barber said administrators in the Boulder Valley district did not learn about the problems until this week when the videos were made public.

Boulder High's principal, James Hill, sent a letter to parents on Thursday asking anyone who had a problem working with Williams to tell administrators or police.

A mother had emailed the head cheerleading coach at Boulder High School, who was out of town at the time, about the technique, sometimes referred to as "breaking."

The head coach downplayed the mother's concern. In an email released by the district, the coach told her that Williams "has done it to the other girls along with many others and has had no issues" but that students don't have to do anything they're not comfortable with.

However, according to Jim Lord, director of the Cheerleading Coaches and Administration Association, the practice is damaging, outdated and rare. He also said he had never heard of the term "breaking."

"While it is possible that some coaches have a perception that this is common within their small circle, it should be clear from the overwhelming number of coaches across the country who have come out against this that it is not a common occurrence. If anyone still harbors that opinion, this incident should help make it clear that it is not acceptable," he said in a statement Friday.

Williams graduated in the spring from the University of Colorado and often performed tumbling tricks before football games there. In a TEDx talk at the school last spring, he spoke about how a mentor he met while growing up in Chicago helped him develop his tumbling talent and how his skills provided an escape from a difficult childhood.

Cellphone video shows 13-year-old Ally Wakefield pleading "please stop" nine times as she's forced into the splits by her cheerleading coach.

"I was just thinking it was normal, I didn't think much of it," Ally told CBS This Morning.

But the high school freshman suffered from torn muscle tissue and a pulled hamstring and is receiving physical therapy.

"The doctor said 100 percent that the injury that she sustained was directly caused by the coach's knee on the back of her thigh forcing it the floor. She said that it could possibly fracture the pelvic system and reproductive organs as well," her mother, Kirsten Wakefield, said.

Wakefield told CBS Denver that her daughter said Williams said not to show anyone the video.