The extermination activities of the Einsatzgruppen generally followed a standard procedure, with the Einsatzgruppen chief contacting the nearest Wehrmacht unit commander to inform him of the impending action; this was done so they could coordinate and control access to the execution grounds.[166] Initially the victims were shot, but this method proved impracticable for an operation of this scale.[167] Also, after Himmler observed the shooting of 100 Jews at Minsk in August 1941, he grew concerned about the impact such actions were having on the mental health of his SS men.