A police officer in Hurst, Texas has been place on leave after cell phone video showed him kneeing a teen in the back of the head.

Assistant Chief Steve Niekamp said that the department was investigating video in which Officer Disraeli Arnold apparently knees the 17 year old and then admits it to the camera operator.

Kelly Pope, the mother of Andrew Pope, acknowledged that her son was struggling with Hurst Officer Miguel Jiminez, who was calmly talking to the teen while trying to arrest him at Bellaire Park on a warrant last week.

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That’s when the video showed Arnold rushing into the scene.

“He [her son] knows that he handled it badly at first, that he should have been a little more cooperative,” Kelly Pope told KXAS. “But, you know, the second officer — there was no reason for it.”

“He comes up at a jolting sprint, kneed him in the back of the head and, as you can see on the video, he says, ‘If you move I’m going to fucking kill you,'” Pope said.

As Andrew Pope is being escorted to the police cruiser, Arnold taunts the camera operator.

“You got it on tape?” he asks. “Arnold, [badge number] 654!”

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In a statement, the department said that it had concerns about the officers actions, including the physical attack, the profanity and the behavior in front of the camera operator.

“This is not behavior that the city of Hurst or the Hurst Police Department promotes or condones,” the statement said.

“You can’t help but be embarrassed — not only for the officers that work in our department, but for anybody in the law enforcement profession,” Niekamp admitted. “You just expect when an officer shows up, they’re going to be in charge. You don’t want the foul language, anything that looks like it might be overreaction. You just want to be professional, calm and in control of the scene.”

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Records released on Monday showed that nearly all of Arnold’s assessments in the last four years indicated that he exceeded police standards, but “Officer Arnold’s enthusiasm may make him overzealous at times, which can cloud his judgment when it comes to policy, procedure and tactics. Sometimes he needs to step back and see the big picture and risks involved.”

Kelly Pope said she planned to file a formal complaint on Tuesday.

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Watch this video from KXAS, broadcast Nov. 27, 2012.

View more videos at: http://nbcdfw.com.

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Watch this NSFW video, uploaded to YouTube on Nov. 23, 2012.