How can I help this puppy?

Our neighbors who I very much dislike already adopted a puppy a few months ago.

They’ll leave poor Mustang outside for hours at a time, redardless of the weather, with no food or water.

It was 90 degrees outside, & we found the poor thing half-strangled by his leash. Again, no food or water.

So we took it some, untagled him, & came back inside. A few minutes later, we heard a knock on the door. We opened it, & the neighbors had returned the food & water. I went down to check on Mustang, & he still had none.

So, the assholes neighbors are obviously home, & they’re purposely neglecting Mustang. It’s now storming outside, & they still won’t bring him in. We called them, & they wouldn’t answer the phone.

What should we do? He’s such a sweet & lovely dog, & I hate to see him suffer….