All any of us could do is guess. It may be nothing, or it may be that someone has used your account or IP for something nefarious. if you have wi-fi, or have friends or family sharing your computer, perhaps someone was involved in something they shouldn't have been. Perhaps it was a Craigslist sale gone bad? Perhaps it was an allegation of threatening emails? Perhaps an "oops" in the IP address?
No one hear can assuage your fears or affirm them as we have no way of finding out.
YOU know if you have done anything that might be illegal, we don't. If you have done nothing, then you probably have little cause for alarm.

