Not much is known about Big Tiny's past and his real name isn't revealed. He is a prisoner at the West Georgia Correctional Facility who apparently ended up there due to being in the wrong place at the wrong time. While his size is intimidating, Tiny isn't a violent man.
As the zombie apocalypse unfolded, Big Tiny and a group of his fellow prisoners survived for months after being locked up in a cafeteria as a riot broke out within the prison. While the guards and other prisoners were all eventually killed off, he remained relatively safe with enough food to last him for several months. It would be ten months before he saw another living soul besides his fellow inmates when Rick Grimes and his group of survivors entered the prison.
Rick informed Tiny and the others about their situation and they were stunned to learn that the world had ended. Rick offered to lead the prisoners to a safer area in exchange for half of the remaining food stores and Tiny was willing to listen to Rick's instructions, trying to be the reasonable one among his group of unreasonable men.
As Rick and the prisoners try to fight their way through a corridor full of walkers, a zombie that's missing a hand attacks Big Tiny from behind, scratching him across the back with an exposed wrist bone. Rick kills the walker and sees Tiny's wound, realizing that Tiny is infected and will eventually turn. Tiny tries to reason with Rick and convince him that the wound isn't serious, but is then suddenly and violently murdered by Tomas who smashes Tiny's head in with a crowbar.