these are trainers :) Keep some you know where are to hone weapon skills and refresh your food materials and so on.

But if you need to get past one, shoot it first or zerk in and smash it then deal with the guys. The other way around won't work unless you are way overpowered for the enemy (basically can one shot them on the way in). It should be obvious, ... big glowy thing on the floor. Did you not ever find a skeleton one in the BF crypts?