You lived in the apocalypse, everyone you knew has either died or been turned. So you were alone, defending yourself since the virus had broken out. You'd come across a few people before, but you always ended up alone.

Coming across a huge abandon prison looked promising right? You walked up to it, inspecting the gates before climbing over without a thought. Yet the walkers emerged quickly and you panicked. Running into the empty looking prison and into the tunnels. Bashing into Carl.