Esbern was behind my character as we were trying to make our way out of Riften, when he suddenly cast a storm atronach and was madly shotting fireballs. Town folk were hit and the whole place went ballistic. Vendors died. Re loaded. But what happened? Crazy ol blade?

I have had an issue before where, after getting him out of the ratway, I couldn't fast travel because there were "enemies" nearby. Once I moved a little ways into the town, it became normal.