From 1935 to 1937, he was head of the Gestapo in Breslau. 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. 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. After a short time as head of the Gestapo in Katowice in 1940, he worked as Chief of the "SiPo" and the SD (, IdS) in Stettin.