Not seeing any documentation of what that's a picture of, I'd assume it represents one of the many cases where partizans were summarily executed in the field under the authority of the military. A partizan is someone who, absent uniform, is working with the enemy of the occupation force, in this case, I'm assuming, the Soviet Union (NKVD).
War is a terrible business, and summary execution of captured partizans wasn't unusual. I guaranty that our allies, the Soviets, engaged in it, too, and likely with less care as to who.
At any rate, that doesn't appear to be an action that took place in a concentration camp.
