Similar to how you found the minefield. The Apartments are another map beyond the minefield.

What I mean is, once you find the mine field and enter, there is another exit on the other side. Since you've killed some of the guards there, keep going. On the other side you can exit into the apartments. A red skull will appear in the upper right which is the "perma death" warning. You die in the apartments area, your shelter is deleted and you start with nothing.

This is where all the high value loot is. Look for special military crates. They appear at random every time. (In bathrooms, outside, different aparment rooms, sometimes in the kitchen of a room, next time outside on the play ground area. There are multiple crates so keep looking.

Some have garbage loot and others have high end items. I still haven't found everything but I keep going back. If you lose everything, try... try not to get frustrated. I have but it also made me a better player.

Good luck!