attacked by German Shepher

Question
I live in a new area where not many of the house are occupied yet including mine - i went over tonight to work on clearing the lot and was doing so with a tree branch lopper - about 2 feet long clippers - my neighbor has several dogs one of which is a German Shepherd - i was only in my yard area for a few minutes when this dog came tearing across their yard into mine - no full fences up right now - it had a muzzle on and is usually locked up in a pen which appears to be about 6 or 7 feet tall near the house. In any event the dog charged me and ran into me trying to bit me through its muzzle - it retreated and attacked me 4 more times - I was terrified I have never been attacked by a dog before and in fact most animals love me. My heart was racing and I was shaken and teary. It frightens me to think if a child had been attacked like that by this dog or if i had to defend myself further by hitting the dog - which I did not do even though I had the metal cutters in my hands. The community style of fencing is only 4 feet tall behind my lot and also on theirs I am very afraid that the height of fence will not restrain this dog and they were obviously physically unable to keep it restrained or control it - and I imagine there is a reason why it wears a muzzle. The female owner came and spoke with me twice while i continued to work in my yard - after the dog was put back in the pen - and assured me this would never happen again. I feel very fearful of their ability to control the dog and that it is obviously aggressive and very territorial - considering i was not in its yard - was in fact over 100 feet away nor was i near any of its family members nor making any aggressive action towards it when it attacked me. I am concerned also that when they landscape their yard they will let the dog roam free in it and that the 4 foot development fence nor the current enclosure may not be tall enough to keep this dog in. I told the owner that despite her reassurances i was contemplating filing an incident report with the proper authorities - I think probably animal control. She was quite upset about that - they are nice people and i am sure sincere but perhaps they have no real idea how to deal with an animal like this - their other dog is a Yorkie and they also just adopted a lab bull dog cross puppy. She did tell me it was neutered just recently and that only her husband or adult daughter can control it - her daughter was the one that was unable to catch it or to get it to stop attacking me. So my question is - is this common behavior and how high can they jump? Any other suggestions.

Answer
No that isn't typical of German Shepherds.  Most of them are friendly and many are big wimps.  However, some are a big problem.  

You are correct that one could easily jump a 4' fence, and some might jump a 6' fence.  

The people have a big problem that is outside my experience to solve.  I hope they letting the new puppy meet strangers and learning to be friendly.  Nobody likes conflict, but you may have no other choice but to contact the authorities if they are unable to control the dog in the future.  Dog owners should not expect people to tolerate a dangerous dog.