A video of a youth being beaten inside the Sylmar Juvenile Hall last year has resulted in charges filed against three probation officers, the Los Angeles County District Attorney’s Office announced Monday.

Deputy Probation Officer Carlos Portillo, 39, was charged Monday with two counts of assault on an inmate. Last week, the district attorney’s office charged deputy probation officer Sergio Cano, 45, with one count of assault. Deputy probation officer, Timothy Boundy, 42, also was charged last week with three counts of assault. All three have pleaded not guilty.

Although the sound is muted in the video, the image shows an inmate being beaten inside a holding cell at the Barry J. Nidorf Juvenile Hall in Sylmar. The video was released by the criminal justice journalism site Witness LA.

Portillo is accused of hitting the non-combative 17 year old in April 2016, while Boundy allegedly held him on the ground as Cano watched. The young inmate reportedly suffered moderate injuries, according to prosecutors.

“The probation officers charged in this case were entrusted with the safekeeping and well-being of youths while in their custody,” Los Angeles County District Attorney Jackie Lacey said in a statement. “Sadly, in this instance, we believe the defendants abused their authority and broke the law.”

Los Angeles County Probation Chief Terri McDonald said in a statement last week that her department initiated an internal investigation that has turned up seven other use-of-force incidents.

“The Department is pursuing administrative action against employees involved in these incidents,” McDonald said in the statement. “Much of that action is pending and the Department cannot comment further on it at this time.”

She said training will be revamped, among other systematic changes.

“The vast majority of our hard-working employees consistently demonstrate their commitment to our clients and our communities, but we will hold accountable those who do not uphold the Department’s values,” she said. “The Probation Department will not tolerate abuse of those in our charge.”

The probation department found that both Portillo and Boundy allegedly had assaulted another teen in February 2016 after he tried to leave his room. Boundy also is accused of grabbing another teen and hitting him in October 2015.

If convicted as charged, Boundy faces a possible maximum sentence of more than four years in state prison, while Portillo faces almost four years and Cano could receive a three-year prison term.

The county’s probation department — the nation’s largest — oversees 1,250 youths at three juvenile halls and 13 probation camps.

But the department has a history fraught with scandal regarding its juvenile facilities. Last year, the department emerged from six years of federal monitoring by the U.S. Department of Justice in response to reports of abuse and poor conditions in juvenile camps. In 2010, the county settled a lawsuit filed by the American Civil Liberties Union alleging there was a failure to provide a constitutionally adequate education to youths at the Challenger Camp in Lancaster. Under the settlement terms, the probation department is now working to improve education there.