Sibling in law being abused

Location: Utah.Hello! My sibling in law is being physically abused by their parent, me and their adult sibling are wanting to possibly gain emergency custody until they are an adult, which is soon. im just wondering how to go about this and how i can do it before parents are notified because they and we fear for their life if they go back home!! I was going to call the free legal services tomorrow but i have to wait until after the weekend to call the courts to try and file. Basically what im wondering is how can i speed the process up and how can i ensure we have enough evidence to for sure get custody!! Im just so so so worried for them and i really dont want to force them to return to that situation, they are staying with us for now but we dont know how long that will last!! We dont have any police reports or pictures of anything but we have multiple witnesses who saw it!! Idk if we can do anything but im willing to do absolutely anything to save this child it breaks my heart what they are going through and I REALLY REALLY DO NOT WANT THEM RETURNED TO THAT AWFUL PLACE!! pls give me some advice!!