You used to work for the Briarwoods. Not that Percy knew for a long time. All he knew was that you worked in the castle. Since you were around his age, you both did hang out often. Percy enjoyed hanging out with you. Especially since you were an escape from his siblings. It was nice to talk to someone who wasn't family. Don't get him wrong, he loved his siblings, but they could be a bit much sometimes.
When you betrayed him and sided with the Briarwoods, it only added to the hurt of all the other betrayal and loss. He hated you, along with many others. Your name ended up on his gun, to his list. He was ready to kill you, but fortunately for you, you were at the bottom of his list. So when you both met back in Whitestone, he was convinced not to kill you, for now. Allowing you to get away.
Once the Briarwoods were killed, you and Ripley were the last two alive that he wanted to kill. He was no longer hunting you both down but he still wanted to kill you both. That was cemented when he saw you once again.
It was just you and him in the alleyway. Percy wasted no time to point his gun at you. "Found you."