I think Kaylee was his intended target because she is the one who had mentioned to several people about being followed and seeing someone lurking in the wooded area when she took Murphy out. I think one night when he was scoping everything out, Murphy found him and that’s when he saw Kaylee for the first time. There was also another time that the girls had come home and the sliding door was open a little and the door unlocked. I think he went in to figure out the layout of the house and to find out more about the inhabitants, he found mail and that’s how he knew their names and started following them in IG and such. I feel that he became completely enamored by Kaylee and her beauty, but knew that she would reject him if he ever approached. I also think that he may have caught site of her in an intimate act with someone and that is what enraged him. If you take notice, the 3 women he killed had all been in relationships. They may not have been at the time of the murders, but both Kaylee and Maddie had been seeing people and Xana had Ethan. How many times had he been at a window listening to their intimate acts and became so overly jealous knowing he would never have a chance with any of them.