Shortly after the outbreak of the Second World War, Adolf Hitler began a program that involved the selection of a particular group of people for extermination. They were people he considered undesirable and dangerous. First, they were transported to special facilities. Upon arrival, they were told to undress and then led into a room designed to look like showers. Once they were all inside, the doors were sealed and carbon monoxide gas was released into the chamber until all were dead. Afterward, the bodies were removed and burned.