on our island. What a jerk.
He built way way up - like over 500 meters. The only way i could get up there was with my jetpack. THen he was throwing out self-replicating items. That made a really awful noise.
I had to call for linden help. They showed me how to ban him from all the estates (property) I own. And how to return all his crap. Good to know for future disturbances.
To be on the safe side I turned off building and scripting for awhile. Hopefully he will get bored and go elsewhere (he = male avatar)