I found this guy griefing on Australian CTF. He destroyed the main buildings and i have some pictures to prove it. Though it might not be enough. piercebob is his name. He leave's as soon after he is discovered. Hope this helps!
Hey Force. I'll pass this on to Kaizo and Lavalord for you. In future, you can use the #kag.aus channel on quakenet to contact us with issues regarding griefers. :P
I'd love to see some stronger evidences. Leaving open in case that anyone wants to upload some video of him.
I hope you reported him on the watchdog. If not then it doesn't help much as not many people knows his greifed.