As a parent and now a grandparent, the thing that has stayed with me about this while thing (the shooter and his motives, etc.) is something I read the mom said or commented on.
I read somewhere and I'll try to find the source but it's been a few days, where the family member or the mom said something to the effect of "he was into his games and internet and even went as some sort of meme once for Halloween when he was in high school" and was just so oblivious and hand-wavey about the whole thing. Clearly no real oversight or discipline into how he was raised with respect to technology. That screams to me either laziness or apathy, but either way, a very dangerous way to raise kids in the social media/internet dsytopian timeline.
Like many kids, if he maybe had more attentative caregivers who moderated and policed his online behavior and activity as a youth and teen in those developmental years, maybe some of the internet-induced mental illness could have been avoided.
Then again, maybe guys in their late 20's and 30's end up breaking their brains on the internet on their own and it was inevitable. I truly don't know.