"YOU" would seem to be the set of social peers, especially the young women, who rejected him because he didn't fit in, because he couldn't fit in and would never fit in, this owing to his disturbed thinking, personality, and behaviors. This psychopath has been on a downward spiral for a long time, which gained momentum rapidly over the past 6-12 months. There were signs all over.
The frustrations of a guy who isn’t getting laid at that age, when he knows most everyone around him are is pretty ENORMOUS (not to excuse him or anything), obsessing about the guys that actually are having sex with the girls he’s stalking - I think deep down that may be the real core root.