I dont remember the whole story although I think that his murder was allegedly orchastrated by Chuck Nicoletti but the problem was that the hit wasnt sanctioned by the Outfit and allegedly thats why Nicoletti was later shelved.

In addition, the German's real mentor was Phil Alderisio since at first the German acted as his bodyguard and driver. When Alderisio went to jail, the German took orders from Nicoletti.

Also if im not mistaken, the German once allegedly stated something like "im the boss of this crew" or something to that extent, meaning the guy was feared by everyone.