LOS ANGELES (CBSLA) — A Los Angeles police officer plead not guilty to one felony count of assault under color of authority on Thursday, after an on-duty beating of a 28-year-old man in April.

Frank Hernandez, 49, was charged on Tuesday. He has reportedly been with LAPD for more than 20 years and has been involved with three on-duty shootings. He has been stripped of all police powers and has been assigned home.

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If convicted as charged, Hernandez faces a possible maximum sentence of three years in county jail.

“This is a disturbing case of the illegal use of force at the hands of a police officer,” District Attorney Jackie Lacey said. “In this case, we believe the force was neither legally necessary nor reasonable.”

The confrontation was caught on camera and shared on social media. A civil suit has been filed against the city of Los Angeles and the LAPD on behalf of the victim, Richard Castillo.

“In this case what you saw was the officer punching a man who wasn’t resisting, who appeared to have his hands behind his back or was covering his face at some point numerous times,” Lacey said in a Tuesday interview. “And so that is a case of excessive force.”

Lacey said she was not swayed by the recent swell of public opinion focused on rooting out violent and racist police, but Castillo’s attorney said the charges were brought quicker than normal.

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“A lot of times it gets drawn out for many years, and I think the public right now is at a point where they’re no longer willing to accept that as an answer,” Wesley Ouchi, Castillo’s attorney, said.

According to police, Hernandez and his partner responded to a call of a trespasser in a vacant lot in Boyle Heights on April 27. During a confrontation between Hernandez and the man, Hernandez is accused of illegally striking the man in the head, neck and body more than a dozen times.

In a Tuesday afternoon statement, the LAPD said it was fully cooperating with the D.A.’s office in the investigation and that its own use of force investigation was nearing completion.

“The Department has taken this matter very seriously from day-one and he will be held accountable for his actions,” Moore said.

The Los Angeles Police Protective League, the union that represents more than 9,900 sworn LAPD officers, released a statement Tuesday evening that said:

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“While we have a fiduciary responsibility to provide our members with assistance through the internal affairs administrative process, what we saw on that video was unacceptable and is not what we are trained to do.”