I was doing a quest in what I think is called Area 51 army base, and the hud showed one more zed in the closet off of the kitchen. I obliterated everything there and around it with a rocket launcher, but couldn't see or kill the last zed, so was not able to complete the quest. This is the POI that has 2 lookout towers on either side as you go in, a medical tent is the first building in the middle, then there's barracks on the left and mess hall with kitchen and above reference closet. Behind these buildings on the right is a garage with army trucks in it.