When Frank West and a fellow survivor named James tried to convince Cletus to listen to them he tells them that he doesn't trust humans anymore than he does Zombies. He then threatened James and demanded him to stay away from him. James however ignored the warning and proceeded to walk towards Cletus. In response, Cletus fatally shot him square in the chest, sending him flying out of the store. Cletus then pointed his shotgun at Frank and said that he couldn't afford to trust anybody.
After he was defeated by Frank, Cletus surrendered and fled out of the shop in terror to get away from Frank. He admonished Frank for wanting guns so bad that he was willing to kill for them. Cletus then accidentally stumbled into a zombified James, who then attacked and killed Cletus as Frank looked on.
While he dies in the official game, the Wii version Dead Rising: Chop Til You Drop gives the player a chance to rescue Cletus from the fate his canon self suffers. If Frank does, Cletus becomes an ally and opens up the shop to sell guns and will fix his broken handgun.