An Arizona sheriff’s department has opened a criminal investigation into one of its deputies after a video emerged of him tackling a 15-year-old boy with no limbs, according to reports.

The video showed Deputy Manuel Van Santen, an 11-year-old veteran with the Pima County Sheriff’s Department, pinning down the teen.

Arizona prosecutors on Friday dropped disorderly conduct charges against the teen after viewing the video.

Samuel Jurgena, a Pima County public defender, said his client went public with cellphone video of the September incident in Tucson to prompt changes in police treatment of young people in group homes.

"I think everyone feels in my office this cop should not be out here with a badge and a gun if this is how he's treating kids in group homes," Jurgena told The Associated Press.

KOLD-TV reported Thursday night that the Pima County Attorney's Office said it decided to drop the charges immediately after seeing the video, which was shot by another resident.

A worker had called 911 after the 15-year-old allegedly knocked over a trash can and made a verbal threat, according to authorities.

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The teen said he was already on the ground when police got there. The boy did not suffer any physical injuries. But Jurgena said the treatment he endured was nevertheless appalling.

"He does not have the ability to fight back in a way like a normal person would," Jurgena said.

On Monday, Pima County Sheriff Mark Napier called the video “shocking, disturbing, and personally saddening to watch,” but acknowledged that “a short video segment may not represent the complete picture of any incident.”

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Napier said he has authorized a criminal investigation into Van Santen, the Arizona Republic reported. The deputy has been placed on administrative leave pending the outcome of the investigation.

The Associated Press contributed to this report.