I can grab items through invisible walls inside houses. I can also shoot people, but they don't seem to notice me.
This is intentional for now, as it feels better to play this way. Player reach is limited only by proximity, and firearm range is limited only by line of sight. May change this down the line after more testing though. Enemy awareness and aggression is dictated by the alert level, so at lower alerts they are more passive. Still I plan to tune up the enemy AI routines more as well.