CC had it close.
There are patterns. I suspect you will find he has become isolated from his goal (he left med school, was it before he flunked out?), relationship issues, and that those who knew him are not surprised.
The news said his Mom not only wasn’t surprised, but was sure it was him. That hints that he was on this path well before last night.
I was wrong about his stature. I thought he might be short, but instead the shooter was 6’3’.