My neighbors are emotionally and physically abusing their youngest child

I hear the same thing every day, The mom or dad screaming and cursing at the little girl who is no older than 8. Even this morning i heard the mom forcing the little girl to use the bathroom and tell her to "fucking poop" and when the little girl said she couldn't, she went batshit crazy and started screaming saying yes she can and she needs to push. My mom also has heard some concerning stuff such as them refer to her as "motherfucker, and little bitch" and telling her to stfu and we were talking about things we can do but she said we need proof or something. I've also seen the dad pop her in her face, and she's almost always crying. The entire house has a really sad aura and there's almost no laughter ever coming out. T As of now me and my mom are going to confront them