You are definitely have a point about the starting and stopping being the reason for that. I do web development, but it's specifically for a recovery company, and I have been in recovery from alcohol for 11 years or so now. I've seen a fair amount of meth psychosis, and unfortunately my sister is addicted to meth still (18 years now). I haven't spoken to her in 6 years or so because she started getting really insane and did some pretty bad things to those around her. Not violent, but her head is completely gone. She thinks she is the baby the dingos took in Australia back in 1980 (that's where I'm from originally).
So yeah, she would occasionally have semi-sane moments when she got out of jail, but the downhill became quicker and quicker, kinda like this guy. It creates an extreme amount of paranoia, and the feeling people are after you and out to get you. Combine that with a whole slew of weapons and anything is possible unfortunately.
This guy, according to people that knew him, had a violent streak for many years. It's also clear from his FB that he was on a rapid downhill, as the posts get stranger and darker as time goes on. I'm glad they were able to catch on to him in 2017 when he threatened the bank and they put him on a hold. I'm pretty sure if they had not arrested him now, it would only be a matter of time before he committed more violent acts.
I really do hope they look into him for the other shootings....those are within the period of posts that he deleted, so hopefully they have someone pulling up the deleted posts. He had such a wide range of weapons as you mentioned, that I don't think they should rule him out just yet. And Poppyflower, that was my theory about some of the shootings after seeing the photos from late 2014, I'm totally with you on that...MOO