Video footage from an onlooker's cell phone captures a Philadelphia police officer engaging in what at least one defense attorney calls a clear case of police brutality.

In the graphic video shown below, Marcus Warryton is hit repeatedly in the head by an officer's baton, at least once while he's on the ground, according to the Philadelphia Daily News.

Three of the officers involved in the June 4 incident have already been put back on duty. The officer who used the baton is still confined to desk duty, pending the outcome of an investigation by the department's internal affairs division, the paper reported.

"The whole investigation is not complete," Lt. Ray Evers told The Huffington Post. "They're looking at the actions of one of the officers more closely. When it's complete, we will release more information on it."

Evers said the department never releases the names of officers under investigation.

Warryton was charged with two counts of aggravated assault and resisting arrest. At one point, an officer claimed Warryton grabbed for his gun, according to the Philadelphia Tribune. Warryton needed seven stitches to close a gash on his head and ear, the paper reported.

Defense attorney Michael Coard told the Tribune that the officers' actions were unjustified.

"Did they cross the line? No, as far as I’m concerned they obliterated the line,” Coard said. "There was a time when the police had enough fear of the law that they would take you to a back alley with no witnesses to tune you up. Now, even with video cameras and witnesses, even helicopters overhead, they don't give a damn because they know the system protects them."

Watch the violent incident below: