Horst Wessel was an early leader within the Nazi stormtroopers (SA) who clashed regularly with leftist groups such as Communists. Although murdered by a known leftist it seems that the reason for his assassination was more personal than political.
Nazi "Saint" Horst Wessel is Shot in the Head
Hitler is wary of the influence of the Brownshirts particularly after he becomes Chancellor of Germany in 1933 and fears that the armed and semi-mutinous gangs will destabilize his rule.
The SA and the Night of the Long Knives
As it suffers blow after blow on the Western, Eastern, and home front and Hitler becomes more withdrawn Nazi Germany focuses its time and resources on expensive propaganda productions.
Goebbel's Propaganda Machine Goes Into Top Gear As Nazi Germany Suffers Blow After Blow