People are simply born with flaws inside, just like outside.
It's easy to see it if someone is born with 1 leg, but this might just as well be the case in their brain, or any other non-visible part of their body, and affect the psyche. That's why you go to a doctor before you go to a therapist, because it might be something physical. He might have had good parents, or he might have been pampered too much, or he might have experienced something very fucked up at some point. Perhaps he cannot even remember it, but the fears sticks. It's the world, shit is mad, asteroid can hit us tomorrow.
Not protecting him at all here, or other criminals,
but it's pretty uninteresting to just label him evil and be done with it. Fact is, he was struggling with the same things lots of other lonely people struggle with, and some things that even most people have to go through while growing the fuck up: Weird, unfounded, negative misconceptions about themselves and others, not developing because lack of feedback. The little feedback there is, is interpreted upside down etc.. I read a little of his text, where he describes crying in front of some friends, and them taking care of him. He never went to see them again out of shame.
One of his few chances of actual relation other than surface BS.
Anyway, I think something good can come of all this mess he made, and that is putting some awareness around these things up front in society. This discussion is one such thing.
If anyone here are "struggling" with themselves, I can testify as a living proof, that looks doesn't matter when it comes to girls. I have gone from unfunny, self-obsessed 18 year old with huge girl-issues, to a funny, charming 32 year old with no problems whatsoever. I'm now the ugliest guy among my friends, who have to teach and help, and go out on town throwing girls at my few still single my age friends.
Be fun to be around, girls just want to have fun. And they are not Aliens. And most of the time, they are the ones with serious (hidden) insecurities to deal with. Thats all.