i was in pvp once and i suddenly fell over dead for no reason... i then got a message from a gm telling me to log off so they could fix an issue i had sent a ticket about... i know it was a GM since i got the message at the top of the screen as well as in my chat bar... fine and well and all that they fixed y item... i just wish they hadnt killed me to do it... i woulda just logged off
They probably just went to your location and right-clicked on you (maybe to bring up chat window?) while in perfect hide, which triggers normal attack in pvp, and with the stats and gear GMs carry, that 1-shotted you.