Bystanders, blackmailers, and perpetrators: Polish complicity during and after the Holocaust
returning Polish Jews encountered an antisemitism that was terrible in its fury and brutality. The most shocking such episode was the Kielce pogrom – a violent attack in July 1946 by Polish residents of Kielce against survivors who had returned, in which 42 Jews were murdered. The Kielce pogrom became a turning point for Holocaust survivors; it was for them the ultimate proof that no hope remained for rebuilding Jewish life in Poland. The pogrom sounded an internal alarm: during the months that followed it, survivors fled from Eastern Europe any way they could. If approximately 1,000 Jews per month left Poland between July 1945 and June 1946, immediately after the pogrom the numbers spiked dramatically: in July 1946, almost 20,000 fled; in August 1946 that number swelled to 30,000, and in September 1946, 12,000 Jews left Poland.
Yet, the murder of 42 Jews in Kielce, as monstrous and harrowing a crime as it was, was not the only story of murder in the post-war period in Poland. As many as one to two thousand Jews may have been murdered after the war by Poles.2 Kielce, however, was the proverbial "straw that broke the camel's back." Kielce reflected the stark betrayal of a Jewish community that was trying to reestablish itself, at a time when it should have received compassion and sympathy from its neighbors. Those who had survived the Holocaust only to experience murder at the hands of their own countrymen could not bear this additional tragedy.
https://www.yadvashem.org/articles/general/anti-jewish-violence-in-poland-after-liberation.html
Poles Imbibed anti-Semitism With Their Mothers’ Milk