During the daring action, he stayed in Vilnius with a rich landowner named Montwiłł, who lost his son at that time. From then on, he used the surname Montwiłł in conspiracy. In Warsaw, he became one of the most active members of the PPS Fighting Organisation, showing his success in organising the robbery of the Opatów cash register on 6 August 1905. He did not enjoy his hero's glory for long in freedom. Two weeks after the robbery, he and other Pepees fell into a trap set by the Ochrana during a planned meeting of the OKR PPS in Warsaw, at 23 Mokotowska St. Escaping, he fired at himself, and when he had the last bullet left, he aimed a fatal shot at his head. However, the bullet only shattered his cheek.