First of all

to understand what happened to killer, you gotta understand who killer the dog was. Now killer was born to a three-legged bitch of a mother. He was always ashamed of this, man. And then right after that he's adopted by this man, Tito Liebowitz he's a small time gun runner and a rotweiler fight promoter. So he puts killer into training. They see killer's good. He is damn good. But then he had the fight of his life. They pit him against his brother nibbles. And killer said "no man that's my brother, I can't fight nibbles" but they made him fight anyway, and killer, he killed nibbles. Killer said "that's it!" he called off all his fights, and he started doing crack, and he freaked out. Then in a rage, he collapsed, and his heart no longer beat. wow.