[5] In the local SS post in Weiden, he met the future concentration camp commandant Martin Gottfried Weiss.

Under the direction of Weiss, a small SS gang offered protection to speakers at weekend public meetings of the Nazi Party in the surrounding villages.

[5][6] After the Nazis came to power, most of the SS men in Weiden served as auxiliary police officers locally[4] and, as early as mid-April 1933, they were assigned as guards to the Dachau concentration camp, where Baer was subject to military drills, Nazi ideological indoctrination, and hard training in systematic techniques for the terrorisation of prisoners.

At Neuengamme, he participated in the killing of Soviet prisoners-of-war in a special gas chamber and in the selection of prisoners for the so-called Operation 14f13 in the T4 Euthanasia Program.

Near the end of the war, having replaced Otto Förschner as commandant of the Mittelbau-Dora concentration camp in Nordhausen, Baer was responsible for the mass execution of Soviet prisoners by hanging[citation needed].

[1] Baer returned to his home county at the end of the war and eventually settled near Hamburg, living as Karl Egon Neumann, a forestry worker.

[9] After seeing a wanted picture in the tabloid newspaper Bild-Zeitung, a co-worker on Fürst von Bismarck's estate reported that Baer was working as a forester there.