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Sarasota, Florida -- A video that appears to show a police officerinjuring ahomeless man during an arresthas sparked an internal investigation at the Sarasota Police Department.

The video -- captured by a downtown Sarasota security camera last month-- first shows a security guard at a bus terminal getting into an argument with Roger Alan Fields.

WATCH:Security video of the incident

The guard eventually forces Fields to the ground and holds him there for several minutes until two uniformed police officers arrive.

Fields is sat down in a nearby chair and several more minutes pass. The video then shows Officer Derrick Gilbert walking over to Fields and putting his hand on Fields' shoulder. Fields appears to pull away slightly, but then the officer immediately forces him up and throws himface-first into a wall.

The Sarasota Herald-Tribune reports Fields had his head split open and was taken to the hospitalto get stitches.

At the time, Fields was charged with disorderly intoxication in a public place, and resisting an officer: obstruction without violence.

On Thursday, City Manager Tom Barwin said he contacted SPD to immediately openan internal affairs investigation.

Officer Gilbert has been placed on administrative leave during the investigation.

Sarasota Police has recently been under fire for its treatment of the homeless.Earlier this month ajudge threw out the case of ahomeless man who was arrested for charging his cell phone in a public park.

The arresting officer told the man at the time of his arrest that "theft of city utilities will not be tolerated in this bad economy."

The ACLU, meanwhile,claims thepolice department fosters a "culture of contempt and abuse" toward the homeless and that officers had been known to engage in what they would call "bum hunting."

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