What happened to Moshe that caused a great change in him?

In Chapter One, we learn that the Hungarian police arrested Moché and other foreigners and took them away aboard cattle cars. Later, Moché returns to report the exiles were systematically machine-gunned in the forests outside of Poland. The malicious murderers made sport of tossing babies into the air and taking target practice. Moché survives because he was shot in the leg and left for dead.