[4] Born in Düsseldorf, Eupen received a law degree before World War II similar to other notable members of the Nazi Party such as Hans Frank, head of the semi-colonial General Government.

Before the German occupation, the mega quarry was owned by the Polish industrialist Marian Łopuszyński who built a railway track connecting the mine with Małkinia–Sokołów Podlaski junction.

Setting up a penal colony there was the idea of Sturmbannführer Ernst Gramss who first ran it as his own personal business venture in occupied Poland.

[4][7] Eupen was in charge of Treblinka I officially from 15 November 1941 (date of the camp's founding by Warsaw SS Governor Dr. Ludwig Fischer), until its closing on 23 July 1944.

[4] Reportedly well-mannered,[4] Eupen nevertheless had a reputation of a notorious sadist who often personally executed prisoners,[6] "taking shots at them, as if they were partridges" wrote Franciszek Ząbecki, the Polish station master.

[citation needed] On 13 December, the Germans launched operation "Schneesturm", which was aimed at liquidating Soviet partisans staying in the vicinity of the Sancygniów forests, attacked from three directions, from the Mountains through Lipówka to Teodorów, from the side of Działoszyce and from the side of Książ Wielki through Janowice and Rzemiędzice, they pacified several surrounding villages, m.in Trzonów, located 6 km from the assassination site, Bugaj, Gaik-hamlet Zaryszyna, Sadek and killed at least 64 inhabitants of these villages and burned many buildings.