The Spartacist Uprising
The Spartacist Uprising took place from January 5th to January 12th 1919 in which German Communists tried to overthrow the Weimar Government and set up a Communist Government like the one in Russia.
In response, the Government asked a group of ex-soldiers, called the Freikorps, who hated them to crush the uprising. Although they were loyal to the Kaiser, they helped the Government to crush the uprising as they hated communism.
However, apart from the 150 deaths in Berlin (and the 400 killed if the suppression of the other communist revolts in places like Bavaria are included), the leaders of the Spartacists, Rosa Luxemburg and Karl Liebknecht, were murdered.
The Government had to decide whether to keep the Freikorps happy and ignore the murders (as it was possible they were responsible for the murders) or to investigate and arrest those responsible so justice would be served.
In the end, the Weimar Government decided to set up an investigation and asked the Police to arrest those responsible for the murders. Four months later, on 1 June 1919, Luxemburg's corpse was found and Otto Runge (who knocked out Luxembourg and Liebneckt) was sentenced to two years in prison for "attempted manslaughter" and Lieutenant Vogel (who may have shot Luxembourg) to four months for failing to report a corpse. Vogel was able to escape to Switzerland before serving any significant amount of time.