Personally, I am leaning away from this scenario for several reasons.
First, he chose a school for his latest hit. That is out of character of the other more random sites. That says to me he has an agenda beyond just killing.
Second, the last two shots were body shots while the first five were head shots. He must have known there was a good chance the body shots weren't kill shots, especially after the first one.
Third, he/they seem committed to escaping. They also appear to be reacting to the situation by moving and slowing down the attacks based on police activity.
Bottom line is, like everyone else, I really don't know and I am just speculating.
He is hunting, that seems to be the pattern. Clear and easy shots. Goes on about his business after that. Probably lives alone and has a job that requires he drives a Utility van. Doesn't work on weekends.
He's crazy, and we can't rationalize crazy.
sw