Reading this thread it seems clear to me that everyone agrees that the key here is exercise and training. (But remember he is still only a puppy.)
Aggression and attacks by GSDs on people is due to poor handling and training. Problems arise when an owner allows the GSD to believe he is pack leader over humans and or does not give the GSD with the mental and physical daily exercise they need to be stable. A walk around the block, or playing in the back garden is just not good enough for them. You must be authoritative over the dog in a calm, but firm, confident and consistent way. A well trained*GSD is for the most part generally good with other pets and excellent with children in the family. But they must be firmly trained in obedience from an early age. GSDs who have passive owners and whose instincts are not being met can, become prone to fear biting. They should be trained and socialized from an early age. GSDs will not listen if they sense that they are stronger minded than their owner, however they will also not respond well to harsh discipline. (Please do not use that shock collar)The daily exercise must always include daily walks to satisfy the dogs migration instinct. If under-exercised and or mentally challenged, the GSD can become restless, destructive And Aggressive. GSDs Do best with a job to do.