From 1941 onward, the SS murdered entire groups of inmates in an organized manner. In conjunction with the "Action 14f13" campaign, a total of 571 sick and incapacitated inmates were murdered at the "euthanasia" killing centres of Sonnenstein (Pirna) and Bernburg. Most of them were Jewish inmates. The largest mass murder of Buchenwald was perpetrated by the SS in cooperation with the Wehrmacht and the Gestapo. In a repurposed horse barn not far from the camp, the SS men of "Kommando 99" murdered at least 8,000 Soviet prisoners of war beginning in late 1941. In addition to such organized murders, the SS at Buchenwald also carried out executions for the Gestapo. Pharmaceutical companies and medical institutes also used the extra-judicial space of the camp for their own purposes. Together with the SS, they mistreated inmates by performing human experiments.