Heinrich Himmler during a Visit to Belarus

This picture was taken by Walter Frentz and it showing Reichsführer-SS Heinrich Himmler and his entourage with local peasants whilst touring the operation zones of the Einsatzgruppen, Belorussia, 15 August 1941. In the center is SS-Hauptsturmführer Werner Grothmann (Chefadjutant von Reichsführer SS Heinrich Himmler), while at right is the translator (because Himmler and Grothmann did not speak Russian). During a visit to Minsk, Himmler attended a demonstration of a mass-shooting of Jews in Minsk arranged by Arthur Nebe (Kommandeur Einsatzgruppe B) after which he vomited! Regaining his composure, Himmler decided that alternate methods of killing should be found. He told Heydrich that he was concerned for the mental health of the SS men. Himmler turned to Nebe to devise a more "convenient" method of killing, particularly one that would spare executioners elements of their grisly task. Murder with carbon monoxide gas, already in use in the Reich as part of the euthanasia program, was contemplated, but deemed too cumbersome for the mobile killing operations in the east. By November he made arrangements for any SS men suffering ill health from having participated in executions to be provided with rest and mental health care.

Source :
https://en.wikipedia.org/wiki/Arthur_Nebe
http://forum.axishistory.com/viewtopic.php?f=38&t=146826&p=2007194#p2007194
http://www.theholocaustexplained.org/ks4/the-final-solution/from-invasions-to-murder/why-did-hitler-order-the-invasion-of-the-soviet-union/#.VvhKZjEprgw