After the war, he joined the Sturmabteilung Roßbach, a paramilitary organization of the Weimar Republic that was unrelated to the commonly known SA.
Thereafter, he was commander of the Führerschule of the Sicherheitspolizei and the SD, an institution that trained future leaders of the Schutzstaffel (SS), Sicherheitsdienst (SD), and Sicherheitspolizei (SiPo), in Berlin-Charlottenburg until March 1941.
[1] Hellwig was the instructor and commander of one of the Einsatzkommandos of the Einsatzgruppe under Udo von Woyrsch, which prepared the Gleiwitz incident as part of Operation Tannenberg before the Invasion of Poland.
[2] After a short time as head of the Gestapo in Katowice in 1940, he worked as Chief of the SiPo and the SD (German: Inspekteur der Sicherheitspolizei und des SD, IdS) in Stettin.
Under his leadership, as part of anti-partisan operations, the SS and police destroyed 108 villages and killed another 2,336 people.