Passing on what I was told in by someone at the event:
The issue wasn't shooting people at the event, nor showing up and being verbally aggressive. The issue seems to be that a number of his statements in local were heavily profanity-laden, and some apparently abusive towards CCP employees (not the actors, but employees). This, is my belief, is where the GMs drew the line - excessive spamming of profanity in local by a single character has always been a quick path to a mute, if it happened to be petitioned or otherwise brought to a GMs attention. In this case, all the necessary factors were present.