There are some very interesting twists and turns on this one.
1) He has zero internet presence beyond a sex site.
2) He had been collecting unemployment, which means that somebody had to have employed him for the minimum time (base period), but no mention of who employed him.
3) He dropped out of the graduate program about 1 month before the shooting spree.
4) Within a week before the shooting he was socializing in a bar with people who knew him, one of whom said he was acting normal.
He was working at McDonalds after he graduated and couldn’t get a job. I’ve seen that several places.