I'm banned??

Today 2 horde was in Goldshire and they attacking my guild mate and also killing Goldshire NPCs. When I tried to help him. They attacked me, and I click alt + f4. When I tried to logon. It says connecting then Disconnect from the server. Character name Zhao(I don't remember horde players names). If that was GMs why they would kill NPCs? And why I can't login anymore? I tested my connection it was not the problem also restart pc and checked for all common issues that can make my computer to lag.