I'm pretty sure it was just something the brother made up to mess up Chase's head, he didn't actually do anything with an animal
Yeah, he didn't, and the doctor knows too that he didn't and that it's a lie... The one that pumps him with several medicine.
That poor dog had to die for nothing
Yeah the brother is the one with the serious issues, because he genuinely (!!!) thinks he's doing Chase a solid, by trying to scare him into taking up casual sex so he can stop taking the drugs (which admittedly are bad for his health).
Chase is just a normal, sexually very inexperienced guy who has been let to believe he turns into a freaking monster during a rut.
Just finished season 1 and I hope that dog thing was a just something he said to mess with his head… and no one fucked a dog in this story