"Grocher claims to have survived nine different Nazi concentration camps during World War II including Buchenwald and Majdanek. He also wrote that he survived the Majdanek gas chambers. When he realized he was led to gassing by the guards, he began walking backwards. The SS man guarding the door to the gas chambers was in conversation with another guard and so Grocher escaped unnoticed, to join his father."

https://en.wikipedia.org/wiki/Mietek_Grocher