[ For a few seconds he just stares at the ground, but then, ]

It's just some stupid shit that happened when I was a kid. Got stuck in a vent shaft when I had to help with maintenance. The engineering crew thought it'd be funny if they left me to stew for a while. They were just screwin' with me, but I freaked out so bad I fucked up my shoulder. That's all--

[ And now he feels ridiculous having said it aloud, and he picks up a rock and chucks it hard at a nearby tree. ]

See? Stupid as fuck.