Tom is a survivor of the outbreak mentioned in The Walking Dead: All-Stars.
Post-Apocalypse[]
At some point early on in the apocalypse. Tom managed to seek refuge at Catherine's Gym. While there he kept talking about how the military is going to blow up the city and that they should all leave the gym to find a better place to live. Everyone thought he was paranoid until it eventually came true.
It's unknown what happened to him after this. Catherine's Gym had been invaded by the undead on numerous occasions so it's possible he died during one of those times, but it's also possible he left the gym to seek refuge somewhere else before the bombs dropped.