DENVER -- Police in Denver are investigating a cheerleading coach after disturbing cellphone video emerged that appears to show a young cheerleader being forced to perform a painful exercise.

Ally Wakefield, a 13-year-old high school freshman, can be seen on video screaming in agony while other cheerleaders held her -- their coach pushing her leg down to do splits.

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She begged nine times in less than 24 seconds for them to stop, reports CBS News correspondent Barry Petersen.

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"What was your feeling when you first saw this video?" Petersen asked Kirsten, Ally's mother.

"I was horrified," she replied. "My daughter showed them to me while I was driving … I almost hit a car and ran off the road."

The coach, Ozell Williams, does gymnastic exhibitions at football games. Williams didn't respond to a request from CBS News, but told a local newspaper the videos were taken out of context and insisted this was normal training for splits.

He and other school administrators have been suspended.

Ally is now under the care of a physical therapist.

"So this really hurt her?" Petersen asked Kirsten.

"Yes, it caused her muscle tissue to tear and her ligaments, as well as pulling a hamstring," Kirsten said.

The incident was in June, but the videos only surfaced Wednesday night.

The school's superintendent released a statement, saying "the images and actions depicted are extremely distressing and absolutely contrary to our core values ..."

The Denver Police Department is investigating the incident and others involving Wakefield's fellow cheerleaders. Late Thursday afternoon, the families met with police in what may become a criminal investigation.