April 5, 1944 - A Jewish inmate, Siegfried Lederer, escapes from Auschwitz-Birkenau and makes it safely to Czechoslovakia. He then warns the Elders of the Council at Theresienstadt about Auschwitz.
At the risk of being picky -- he did not escape "with the help of the SS". He was helped by a member of the SS who was eventually executed when found out to be a traitor to the SS because he was loyal to his Humanitarian principles.