Is it normal for him to be like that?

I believe my nephew cut hair off my dogs tail. It's OBVIOUSLY cut. My mom claims he's not guilty. But I say otherwise.
I live with all my brothers. We currently have a dog and a cat. But we used to have another cat (not relevant). So we get my nephew every Wednesday and every other weekend My mom said that the dogs tail has been like that since last Wednesday.. A coincidence? I THINK NOT. I SEE THE DOG EVERYDAY. There isn't a day I don't! And I'm extremely observant. And I know it's a lie. Anyway, my nephews (ex) step brother used to be a little abusive. And my nephews mother is pretty neglectful and slightly abusive. When he plays pretend with those foam swords and action figure toys, he gets PRETTY violent. He swears under his normal voice and things like that, I know boys are boys. But it's pretty bad. And I find it really concerning. He pees his pants almost every night unless I get him up to go pee before he does it in his bed. He kind of has a history of animal cruelty. Not like choking them, but just being very mean. He used to pour water into the cats food so they could eat soggy food. He specifically said that Nd I asked him if he thought the cats would eat it.. Nd he said yeah if they're really hungry. What kind of child says that??! And I told my mom and she laughed Nd said that little shit! Ha ha ha ha. My mom baby's him. Please tell me his behavior is at least a bit odd!! Is it normal?? Id like votes and comments from people who are therapists or have similar experiences. Thank you.