Originally posted by: Fudgeman
duh, we know that, but the problem is what activated it inside the pit
Anphorus is right. Read the other posts in this topic. Hollows are created by a person's soul chain being eaten away. So far that is the ONLY way that hollows are known to come into existence. Urahara explained in the episode that the only way for Ichigo to become a Shinigami is to place him in a situation where he might become a Hollow. As a result of that test, Ichigo is in his current state.