The photo above was shown in the Dachau Museum from 1965, when the Museum first opened, until 2003, when the Museum was enlarged and changed. This photo was removed because it has nothing to do with Dachau.
The photo currently hangs in the Yad Vashem museum in Jerusalem and according to the museum, the photo was taken by a German soldier in the Polish town of Olkusz on July 31, 1940 during a reprisal action against the townspeople after a German policeman named Ernst Kaddatz was killed by members of the Polish resistance on July 16, 1940.
In the photo, men are shown are lying face down on the ground while German Wehrmacht soldiers in the background smile for the camera. Rabbi Moshe Isaac Hangerman is shown, barefoot and wearing tefillin (phylacteries), as he appears to be praying.
One Jew and two Polish men were killed during the reprisal action and all the men in the town, from 15 to 60, were forced to lie on the ground from early morning until noon as punishment.
The Polish resistance was fighting as illegal combatants; reprisals were legal under the Geneva Convention of 1929.