The growing threat of conflict with Germany added to the crowds, as many army reserve soldiers were ordered to report to their units amid worsening international tensions.

At 11:18 p.m., the dense traffic abruptly stopped when a time bomb planted by a German saboteur named Anton Guzy exploded in the waiting hall.

[2] The saboteur who planted the bomb, Antoni "Anton" Guzy from Bielsko (formerly Bielitz), was the son of a German mother and a Polish father.

[3] Guzy, who worked as a locksmith, joined the Gewerkschaft Deutscher Arbeiter, a local organization that facilitated job opportunities in Germany, after he found himself unemployed in 1938.

[3] Guzy traveled to Tarnów, a Polish town located just over the border from the German city of Gleiwitz, with a man named Neumann.

[2] He left two suitcases filled with explosives in the luggage hall and proceeded to a platform to wait for the arrival of a Luxtorpeda train from Krynica, which passed through Tarnów on its way to Kraków.

At 11:30 a.m., Guzy met a man named Neuman from Skoczów, who was allegedly affiliated with a German saboteur organization.