Randall was a member of a group of survivors that got involved in a shoot-out with Rick Grimes, Hershel Greene and Glenn Rhee in a desolated village. Almost nothing is known about his life from before the outbreak except that he once went to school with Hershel's daughter Maggie. They weren't friends, in fact, they hardly knew each other at all.
After Rick shot two members of Randall's group, Randall along with two others attacked Rick, Hershel and Glenn. The gunfire attracted the attention of the undead locals and the group's driver left Randall and one other behind. Randall was on a roof across the street from Patton's Bar as the walkers began massing and tried to jump down. He fumbled his jump and wound up with his leg impaled on a railing pike. With walkers closing in and not having the time or tools to free Randall's leg carefully, Rick forced the leg off of the fence and he, Glenn and Hershel retreated to the farm where Hershel attempted to treat the wounded youth.
After Randall was patched up, there was a heated debate amongst the group about what should be done with him. Since he knew where the farm was located, some feared that he might tell his friends about it if he was set free, and some even contemplated the possibility of executing him.
In the episode "Better Angels", Shane - having let his jealousy of Rick get the better of him - devises a plan to get rid of his old friend once and for all. He chooses his moment to act when no one is watching him and he frees Randall from Hershel's barn, taking him into the woods and pretending to want to side with his group. As the two start walking, Shane leads Randall behind a tree and snaps his neck off-screen.
Later on, after Shane has lured Rick off the farm in order to kill him, Glenn and Daryl are looking in the woods trying to find Randall. However, Randall finds them, having turned into a walker. Daryl manages to kill the zombified Randall with a machete to the head, but upon examining the body more closely, he finds that there are no bites and is left wondering how Randall could have turned.