8 year old step son said uncle took pictures of him naked Update

I have 2 step kids. 13 and 8. I came into their life when they were 5 and 10. I'm basically a second mama to them. They even call me mama. My step son is very shy and very quiet. He likes to play by himself. Doesn't have any friends at school and just was diagnosed with autism. My dad's brother lives with him and my mom. I didn't grow up seeing my uncle that much. He was in prison for years for vehicular manslaughter when he was drinking and driving. He killed a 16 year old boy. I never really knew him but my dad always had good things to say. We are supposed to go there and spend Thanksgiving but my step son didn't want to go and he had been crying and we asked him what was wrong. He told us that my uncle makes him take off his clothes and takes photos of him. He didn't want to talk about it more so I called my step kids bio mom to tell her what was going on and then I called my dad. My dad started defending my uncle saying there is no way that's true. We three-way called with bio mom and she was rightfully losing it. My dad said my uncle said it's not true and we can talk in person tomorrow. Bio mom agreed to hold off calling the police until we all talk tomorrow and he will let us go through his phone. But if it is true couldn't he just delete it off his phone? What if the stuff isn't in his phone? I'm stressed out and my husband is just wants to call the police now but him and his ex are agreeing to hear my uncle out. I'm just stressing and worried and disgusted.

Edit: I planned to just call my dad. I didn't know he would loop my uncle into it or even defend him so quickly.

Update: We did just call the police. We were dealing with that all night which is why I never updated. My uncle is in custody and they're going through his stuff. I planned to update you guys but we were dealing with the police all night