I'd report to the ASPCA,Humane Shelter or even Animal Control. I had a similar situation, a dog was walking along the road, and I knowing how easy they get runned over, was concerned, and got out of my car.
Another passerby did the same thing, we got her collar and sort of held her away from the road, such a sweet, dog.
She was so neglected, eye infection,matted dirty fur, smelled horrible, I called our vet and gave the rabie's tag (expired too) id number, they tracked down who the owner was, while we also called a guy that is the animal control guy for our town, he came looked her over, the owner stopped by and asked if she had been hit by a car and told us the dog was hers, the other lady and I remarked how she was uncared for and had a neglected eye infection, the dumb owner said she didn't have her groomed cause her groomer was sick with cancer. Lame excuse, we told her there are plenty of groomers in our area. Well she took her home to her roadside farm. Meanwhile the guy from animal control asked us about the tags, the 3 of us tried to think of a good reason for him to inspect the living quarters (the barn) and even sneak a peek at her cows and sheep that also are unkept, the expired tags was a valid reason so we were happy. This AC guy and his wife are terrific, his wife even works with cat adoption,they do not take and have the animals destroyed but foster and place them in good homes.
I think this woman got her act together, finally.
The dogs paws were so matted it looked like little spurs at it's heels, full of barn manure and straw.
Sickens me how people can do this to animals and children.