Behavior Issues!

Question
Hi, Please note:
**I have a Male German Shepherd, 2 years old. NOT FIXED!
**I have a Male Pug. 4 years old. NOT FIXED
**I have a FEMALE PUG. Less then 1 year old. IS FIXED!
>>Here is the situation.
Before we brought home the NEW Female Pug, the Male Pug and the Male GS got along GREAT! I really mean....GREAT! They played with each other all of the time. Best Buddies to say the least!
**Now.....Since we brought home the new Female Pug and even after we had the female spayed, we have notice a GREAT increase of aggression from the GS.
**The Shepherd is VERY aggressive toward out Male pug. Several time during the day, we have to keep yelling at him and scalding him for showing his teeth, etc. towards the Male pug. We are worried that he is going to hurt/attack the Male pug.
**The GS is very friendly towards the Female pug!
**When (anyone) now comes to the door. The GS acts like he wants to bite them. Even if he knows who it is. It doesn't matter!
**WE are very concerned about this CHANGE in behavior!
**To the best of our knowledge, we know he isn't sick in any way. We know he doesn't have anything like lyme disease.
>>What do you think is going on here besides the fact that the Male GS is just trying to be the Alpha Dog here?
>>Do you think is we NOW got him fixed, if this would make any difference? Or is it too late for that?

Please help!
Any suggestions would truly be appreciated!
Thanks!!  

Answer
It is really hard to be a 100% sure without seeing your dog, however, this i can be sure of......If you are going to neuter your dog to see if this is the problem you need to do it quicky, After the age of 2.5 it will not help at all..This could very well be the problem. Even though the female is fixed, they can smell her and the GSD wants the pug out of the picture now. Good luck
nancy