Nothing is known about Greely's life before or as the outbreak began, except that he most likely worked at the Army National Guard station with the other prisoners.
After Gene Gavin was killed by Brian Blake, Greely, along with Johnson, Tommy Zorn, Manning, Trey Barker, and Stinson were imprisoned below the racetrack. Sometime later, he was killed and fed to Penny Blake. Tommy later tells Barker that he doesn't want to go through with the plan because he doesn't want to end up like Gene, Greely, or Johnson.
Sometime after being imprisoned, Greely was killed by Brian Blake and was later fed to a zombified Penny.