Arsenal has been thrown in jail.

He was exploiting a bug with pet code. If you initiated combat by having your pet cast an offensive spell on a monster, the monster would not fight back (against either your OR your pet). Your pet would eventually kill the monster and you would gain experience for it. This bug has been around for a long time, which means he's probably been exploiting it for a long time.

I haven't decided for how long yet. Probably two weeks, if not more. It irks me when people find bugs and then they don't tell anybody about it, but would rather exploit it for personal gain.