Sym's screen debut took place in 1925 with the role of Baron Kamiłow in the Polish silent film Vampires of Warsaw (of which no copy is known to exist).

In late 1920s Sym worked mainly in Austria and Germany, appearing with such actresses as Marlene Dietrich, Anny Ondra and Lilian Harvey in silent movies like Die Pratermizzi and Café Elektric directed by Gustav Ucicky.

At the beginning of the war he helped set a trap which caught actress Hanka Ordonówna (who had been Sym's prewar screen partner and a friend from Warsaw's theaters).

[citation needed] Polish resistance quickly learned about this, and a group of agents led by Teatr Komedia actor Roman Niewiarowicz started tracking Sym's activities.

The Nazi propaganda movie directed by Gustav Ucicky told a story about the pre-1939 German minority in Poland's Volhynia, resettled during Nazi–Soviet population transfers.

[citation needed] Sym's collaboration with the Germans contrasts with the conduct of his younger brother, Ernest, who, during his official activities as a chemist, clandestinely produced explosives for Poland's Home Army.

[citation needed] In early 1941, the headquarters of the underground Polish resistance group Union of Armed Struggle (ZWZ) decided to liquidate the collaborator.

Sym's behavior was loudly trumpeted by the Nazis, and his assassination would show the Poles that the underground movement was active, always ready to punish all traitors.

To carry out the assassination, the ZWZ selected the commando group "ZOM" of the Intelligence Department of the Warsaw-City District, led by Bohdan "Szary" Rogoliński.