(NewsNation) — A former assistant football coach at a Southern California high school was sentenced to prison after placing a hidden camera in a girls’ locker room.

David Arthur Riden was sentenced to more than nine years in prison and ordered to register as a sex offender following the incident at Los Osos High School in Rancho Cucamonga.

Authorities placed Riden, 53, under arrest last year after another employee discovered a secret camera disguised as a phone charger in a ladies’ restroom at the school. Prosecutors say Riden used the camera to photograph more than 20 girls while they were in the room.

Attorney Gloria Allred represents 48 alleged victims. She says many feel the sentence is not harsh enough, and that there may be more victims out there.

“There are so many victims, and we don’t know how many there are. Although I represent 48, there are also other law firms involved in representing others. In addition, there may be other victims who have not yet discovered if they have been videotaped,” Allred said.

The San Bernardino County District Attorney’s Office seemed satisfied with Riden’s guilty plea, suggesting it “ensures Riden is held accountable for his crimes and the victims will not have to endure a potentially lengthy trial and any further emotional trauma.”

Lawsuits and damage claims have been filed on behalf of the victims against the Chaffey Joint Union High School District, which reportedly hired Riden back in 2015. Allred said a major concern of her clients has been if the video was placed on the internet — and if it could pop up one day.

“It’s just so devastating to them emotionally. You know that young girls especially are very, you know, sensitive about their bodies and their development. And the idea, especially that someone they trusted, the assistant coach, would betray them is the way the victims put it,” Allred said.

One of Allred’s clients, Jordyn Stotts, identified herself as a victim. Stotts said Riden’s actions “ruined” her and that she no longer has trust in people.

“Once I was a girl who could take on anything,” said Stotts. “Now I am a girl who is scared and who doesn’t know what to do.”

Stotts said she now suffers from anxiety and depression.

Allred is pushing for answers for Stotts and the rest of her clients. She wants to know how long the hidden camera was there, who was videotaped, what happened to the device and if there’s video of her clients on the internet.

“They (law enforcement) did do a search warrant and were able to recover his computer. But, we don’t know what was missing. What we don’t know is sometimes more devastating than what we do know,” Allred said.

For Allred, the case is about finding the truth and figuring out why the camera was not discovered by the school system sooner.

“Parents are very upset because their daughters are upset. They trusted this school, and now they feel that they can’t trust a person that they had every right to trust. They have a right to have a safe, education workplace — because after all, a school is a workplace,” Allred said. “I was a teacher in public schools for many years before I became a lawyer decades ago, and you know, we want it to be safe. And it’s not safe if this kind of thing can happen.”

Chaffey Superintendent Matthew Holton said the school system remains “deeply concerned” about the case.

“Our support for our students is unwavering and we will not tolerate any actions that infringe on their privacy,” Holton said in a statement to The Associated Press.

Prior to his sentencing, Riden pleaded guilty to charges of secretly photographing a minor, possessing more than 600 child pornography images and using a minor to produce such material.

The Associated Press contributed to this report.