SAN DIEGO -- A San Diego police officer accused of brutality against a local homeless advocate will not face criminal charges after a lengthy police investigation.

Last March, David Ross, known as the "Waterman," said he was handing out water when the crowd of homeless people spilled into the street in the East Village.

Ross, 73, said a patrol officer aggressively dispersed the crowd, and when Ross questioned the officer's actions, witness Myron Hill said, "The officer grabbed Dave, threw him to the ground, started kicking Dave, telling Dave to get up, then kicking him again."

Ross suffered a severe concussion and a torn rotator cuff in the incident, and he later filed a lawsuit.

10News learned an 8-month internal police investigation led to no criminal charges and the officer remains on the force.

Lawyers for the SDPD said state law prevents them from revealing if the officer was disciplined.

10News' Michael Chen asked, "Ross' attorneys have dozens of witnesses that will say the same thing. So why are there no charges and why is he still on the force?"

"Our investigation revealed facts inconsistent with the civil lawsuit," said Paul Cooper, counsel to the police chief.

"In the interest of public safety, doesn't the public have the right to know (the facts)?" asked Chen.

Cooper replied, "We'd be reluctant to discuss the case in detail once litigation is filed."

Homeless advocates are decrying the results of the probe.

Rachel Jensen of the Girls Think Tank said, "It's unconscionable. This is such a clear case of abuse of power."

Homeless advocates and Ross both share a feeling of disbelief.

Ross, who recently suffered a stroke, said, "It angers and infuriates me."

Ross said he believes he was mistaken as homeless and is worried what the lack of serious punishment could mean.

"By sheer example, it's encouragement … that other police can do it. It sends a message that the homeless can be treated like this," said Ross.

Ross is no longer considering dropping the lawsuit now that criminal charges have not been filed.