The Pinsk massacre was the mass execution of thirty-five Jewish residents of Pinsk on April 5, 1919 by the Polish Army. The Polish commander "sought to terrorize the Jewish population" after claiming to being warned by two Jewish soldiers about a possible bolshevik uprising. The event occurred during the opening stages of the Polish-Soviet War, after the Polish Army had captured Pinsk. The Jews who were executed had been arrested were meeting in a Zionist center to discuss the distribution of American relief aid in what was termed by the Poles as an "illegal gathering". The Polish officer-in-charge ordered the summary execution of the meeting participants without trial in fear of a trap, and based on the information about the gathering's purpose that was founded on hearsay. The officer's decision was defended by high-ranking Polish military officers, but was widely criticized by international public opinion.
 

The battle for Pinsk was won in March 1919 by General Antoni Listowski of the Polish Army regional commander of the Polish forces in Podlasie. The city was taken over in a late-winter blizzard with considerable human losses sustained by the 34th Infantry Regiment under Major Narbut-?uczy?ski who forced the Bolsheviks to retreat to the other side of the river. Before their withdrawal however, the Russians had raised an armed militia composed of a small, non-representative group of local peasants and young Jewish communists who kept on shooting at the Poles from concealment.
 

An interim civilian administration was set up in Pi?sk, but the hostilities continued. There were instances of Polish soldiers being singled out at night and murdered. On April 5, 1919, seventy-five Jewish residents of the city met at a local Zionist center to discuss the distribution of American relief aid according to eyewitness accounts. Public meetings were banned at the time because random shots were still being heard and the town was recently under Bolshevik control. According to some accounts the meeting had received approval from Polish military authorities. When major Aleksander Narbutuczyski heard, that the meeting was a Bolshevik gathering, he initially ordered his troops to arrest the meeting organizers.   The town commander fearing a Bolshevik uprising, which he did not investigate, ordered the execution of the hostages. Within an hour, thirty-five detainees were put against the wall of the town's cathedral, and executed by a firing squad composed of the Polish soldiers. It was claimed that some men  were stripped and beaten.
 

Sources:

• https://en.wikipedia.org/wiki/Pinsk_massacre