Why did the Nazis kill and torture Jews in the Holocaust?

They blamed the Jews for choking the German economy. The German Jews were a wealthy minority and the Nazi Party needed a common enemy to unite the people, so they used the Jews. For example, if the Earth was attacked by aliens, the people of of Earth would unite against the common enemy. Also, since they were wealthy, they could arrest them, confiscate their wealth and add it to their coffers. Furthermore, Jews were not allowed to own firearms, so they could not resist.