I have a "shitty" situation on my hands!

Here's the deal,my roomate and his girlfriend have this mutt of a dog and the things around 10 months old now but the thing keeps shitting everywhere and the owners r even worse.not shitting on the floor of coarse but the (brett)just passes out all the time and leaves the dog unattended for like a couple of hours and then wakes up and finds that it shit on the floof and beats the damn thing like its his job but does this like its the dogs fault for not going outside thats fucked up right?,thats what i thought.but then the girlfriend(brittany) let me just say she's a blackbelt in tae kwan doe,but she always yells at bret for being mean to it but then they left the dog in their room for like 6 hours and came back to find that the dog ate through an entire 12 pack of sunkist,and im not talkin about tearin the box open im talkin about exploding each pop can inside of its mouth i just think the dog has a chemical imbalance in the head but anyways the dog comes up to greet her and she punts the damn thing like 12 feet in distance and then yells at brett for doing anything about it.well my biggest problem is,well i have another roomate one of my best friends(Brent),r tired of being afraid of bringing our friends over and havin parties cause the thing shits and pisses all over the apartment and well u probably guessed it,it smells like it most of the time,i dont even like bringing my girlfriend over anymore.But i need some advice on the situation cause i really just wanna take my buddys 44 and blast the damn thing cause theres no way the owners r capable of changing the dog since they r just as immature.What do i do NS?