First thing I do is carve out a spot to hide in so I'll be safe when it's night. When daylight comes, then I go out and start gathering wood and other resources for a bed, sword, crafting table, a door and chest to store things in, while scouting for where I want to start building. I also mark where I spawn so I can find it in case I wander far off.
Hopefully they are gone now. I would say rule of thumb..anyone who screws with your server and keeps you from being able to play, ban 'em. You should be able to play and enjoy your game in peace...I hope no one else bothers you..
I'm sort of new to the game but I would say just ban the person. Why even bother taking a closer look at who the player is? You said yourself the player is dangerous and obviously from what the player did on your server...he / she is not a nice person. Just ban them and go on enjoying your game...