You was still under gun point, it doesn't matter if you were behind a wall
right ok this is where my PERP expertise come into play here
if you have a small enough distance between you and a wall to cover yourself and pull out a gun to defend yourself, you can shoot.
the entire idea of fearrp is to not endanger your life; this is not really endangering his life, as he made sure you couldn't just shoot him by ducking behind cover.
I'll try to get a video as a visual presentation of such theory
EDIT: here's an example:
This was from a PERP report on me which was denied, as my actions were deemed as acceptable and not risking my life. You can see I ducked behind cover, over a MUCH longer distance than Pug did, and shot him while not entirely risking my life. Considering PERP has much stricter rules on risking your life, if what I did was fine, then the warning given to Pug was totally excessive.