CHICAGO (CBS) — The lawyer representing the family of a Dunbar High School student seen in a viral video being pushed down the stairs by a school security guard and then hit in the face says he’s shocked by the guard’s acquittal.

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Mark Sutter seemed to think this case was a slam-dunk for the prosecutors who tried school security guard Preston Dixon for battery.

“As a lawyer,” he said, “I’m shocked and disgusted and as a father I am appalled.”

“It’s completely atypical,” he says of the not guilty finding by Judge Peggy Chiampas. “Frankly I’m shocked.”

In the cellphone video, Dixon is seen pushing the then-16-year-old girl down a flight of stairs.

As she’s lying on the ground, he punches her in the face.

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Chiampas, Sutter said, found fault with the alleged victim’s testimony.

But Sutter said the videotape was compelling evidence.

“You know they say a picture speaks a thousand words, then what does a videotape speak?”

“I don’t know,” he said. “I’m completely shocked by the outcome.”

The girl’s mother, Pershaun Goodlow, said: “I was totally devastated watching that video over and over and over again. I was devastated that someone would find this guy to be not guilty.”

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The family still has a civil suit.