The Holocaust started in 1941. Hitler was using his time to execute European Jews during the time of WWII. Between the time of 1941 and 1945 is when Nazi Germany and its collaborators killed and executed around 6 million Jewish people. With one of the camps executing and killing 1,100,000 Jewish prisoners.
And during the Holocaust is not only when they made Jewish people suffer but also split them up from their families. What the Nazi guards would do for fun would be taking hats of prisoners and throwing them over the fence and then when they tried to get them be back they would shoot them.
After the Holocaust ended and prisoners were freed a lot of them did not survive and died because even with care they still could not survive because of how they were treated during the Holocaust. Some people were still able to survive and live a long life and can tell their tales to others.