CPS sexual abuse evidence and the Cops

Both me and my little sister have been sexually abused by my dad. I have a video of him with his hands down my pants. My older sister went to the cops and called CPS. They told my mom to not let my little sister talk to CPS or they’ll take her away and put her in a foster home.

Are they just tying to protect my dad (who was a cop 20ish years ago I don’t know if they know)