This mystery can be found in eastern Hamtunscire, just northeast of the city of Wincestre.
Kill the Bear and Speak with the Man
When you approach the area you’ll hear a man screaming for help, with an upturned cart nearby. You’ll find a note on a rock beside the cart, which you can read for some context about who the man is, and why he might be trapped by a bear. You can then kill the bear and speak with the man, who won’t be too pleased by what you’ve done, since the bear was a source of income for him in fighting pits.
At this point you can choose to fight the man, apologize to him, or reply with a sarcastic “Don’t mention it.” If you choose to fight the man, it will be an easy fight, but you won’t gain anything extra for doing so. Regardless of what you choose, once you’ve dealt with the man the mystery will complete.