Adolf Hitler was sworn in as Chancellor in 1933 under the Weimar Republic. A couple months later, The Enabling Act of 1933 was made law. It allowed the Chancellor and the Cabinet to enact laws without the approval of the Reichstag, the lower legislative house in Germany's government at the time. Hitler and the Nazi Party used the act to advance their goals of turning Germany into a dictatorship. The passing of the act is widely considered to be the end of Weimar Germany and the start of Nazi Germany.

You may be thinking of the Night of Long Knives, an even that took place later. It was a purge that consolidated power for Hitler and the Nazis, and it was justified by the Nazis who said it was a strike against a supposed coup that was going to take place. That of course was a lie, but they claimed it anyway.