A player can see and shoot through buildings, (possibly even walk through). Simply by modifying PBO files inside game directory.
This is game breaking and needs a fix.
Happened twice on one day, in different servers, on public. Me and my friends were killed in this way. It was obvious that the opposing player (who killed us) was utilizing this glitch. He could see and shoot through specific objects and not all objects.
It was all in the eastern area of North West Airfield. Inside the industry complex in front of the single barrack.

This is most likely the same bug as shown in the video added in this report.