Originally posted by Baron von Tansley:

I'm honestly not sure what happened: the pig pen was on one side, trolls in the middle, I was on the opposite side. I'm not sure how to measure distance in game, but I was like, 4 Kilns away from the trolls in an open flat meadow. After I shot the troll, it came at me for a second before turning around to kill the pigs/blow up the pen.

Originally posted by knighttemplar1960:

One wooden floor tile is 1 meter. Trolls have a 30 meter perception radius and a 20 meter alert radius at a 90 degree angle in front of them. If you leave alert radius through distance or angle the troll will attack something else. Their priority after you is live stock (if they can see them), crops, behives, other buildings.

Okay, I think I have an idea of what happened here. You were originally juuuust outside its normal detection range and when you hit the troll with your arrow, you "got its attention". Its behavior pattern had it turn and take a step or two in the direction the arrow came from, but it failed to perceive you or couldn't find a proper pathing for some reason and so just stopped and went back to the next visible priority on its list - in this case, the boars.