Billy's Dad was a crooked cop with a gambling addiction who left him at King's Dominion Atelier of the Deadly Arts to toughen him up. Billy felt abandoned and hated his father for never loving him. On a weekend trip to Las Vegas, Billy planned to kill his father. When his strength was overridden by his father's weight, Marcus Lopez saved Billy by killing his father for him.
When Marcus was later attacked by Chico, Billy attempted to help Marcus and was stabbed in the process.
Billy assisted on the assault on the tenderloin. When Lex's bombs failed to blow open the back door, he climbed through the window to save Saya right before she was stabbed.
Master Lin soon declared that their final exam was to kill all the rats, those that have disobeyed the school's rules. Saya and Willie were not declared rats and attempted to help Billy who was declared a rat. When given the choice, Billy left to be with Marcus and Petra who ran from their classmates as it was safer to be with his own kind, the rats, then to be with Saya and Willie who wanted to help him.
They concocted a plan to kill Viktor. However, when they fight began, their friend Paulie ditched them. Billy was left to improvise and was savagely beat by Viktor. Viktor thought Billy was weak and lazy. Just before he was about to kill him, Billy sprung the trap and a stone pillar crushed Viktor's back. Marcus and Petra arrived and were surprised Billy had gone through so much when Billy told them he was ditched by Paulie. They then were attacked by Dan, and they fled to the last place anyone would look -- the Tenderloin.