dog aggression towards familiar dog

Question
I just logged on because my German Shepherd which is female has for the first time attacked our Chihuahua/Pomeranian which is male, she grabbed him by the throat and began shaking him, she would not let go. When I tried to separate them she snarled at me. She has never displayed this level of aggression towards the other dog or myself, even after the fact when I thought she had calmed down, I had the smaller dog in my arms and she tried to grab him from me, you would probably have the same advice as the question which drew my interest, but just to let the other person know they are not alone.

Answer
It might be a medical problem,such as hypothyroidism,which can cause dogs to do things that aren't normal,so it might be a good idea to have the dog tested for that

It might be jealousy,and the best way to prevent that is to spend a lot of time with the German Shepherd along and away from the other dog,and then slowly let them be together more often

Another thing you might want to try and it works for a lot of people,is to muzzle the German Shepherd(both if you want to)and then let them sort it out,that way the small dog won't get hurt-a lot of times once they figure out who's in charge the fighting stops