It happened on the third floor. Usually when I enter a shop I take it easy, pass a few turns quickly to regain health/mana. This time though, Brax got aggravated for some reason, and killed me in two hits (I was skipping turns quickly, so it took me a few seconds to realize what had happened). I didn't try to steal anything or attack him, so I'm not sure why it happened. It was also a permadeath game so I don't think I've got any save file for it. The only explanation I can think of is that my wyrmling may have targeted him for some reason, causing him to become hostile to me as well. It all happened so fast though; I can't really be sure.
Did you cast anything in the shop? Some spells you wouldn't think of as attack-spells can do minor area-of-affect blasts. There's a radiance level that's mostly a self-buff but zaps anyone near you for a point or two, for example. If you used one of those while near Brax, it would make him go hostile.
I didn't cast anything myself, but now that you mention it, I think I remember a weak enemy with low health running in from the outside and attacking me, triggering the Blinding Flash thing from one of the Vegan skills. The enemy died instantly as a result of the Flash, which is why I went back to passing turns quickly without paying attention. Had the enemy survived for even one more turn, I might have noticed that Brax was hostile and actually managed to save my character. If that's what turned Brax hostile, then that has to be one of the unluckiest ways of losing I can think of, though I suppose I am fortunate that it happened on an early floor as opposed to deep into the game. I suppose the lesson here is to just stand far away from Brax no matter what.
Brax does not appreciate fighting in his shop. Especially not in his vicinity. He really should put up a sign. Cheers! ~FlaH
Blinding Flash hits all eight squares around you. If Brax was in one of them, that's enough to enrage him.
