spoiler alert
I wonder if the prisoner that we didn't see get killed will cause some serious grief to the group (as was the case in the comics). And I don't trust the all-to-friendly prisoner. Something smells fishy...
The prisoner screams as Rick closed the interior door, and continued screaming as the camera changed angles and focused on Rick's face from the front. It's subtle, but you can hear him screaming the whole time.
edited for clarity.