>

I mean, it seems obvious to me, but when you get depressed and nihlistic at the hopelessness of everything - you either turn it inward or outward.
Also the rise in mass shooters seems to roughly coincide with the decrease in serial killers. I think some a lot of it is the news covering mass shooters so much more than serial killers. 
While many say the psychology is not the same. People imitate what they know. How many would have taken the steps to go though with that form of violence if they hand been exposed to it so much. >

The other key distinction that might explain the rise in one and the decrease in the other is probability of success.  
It has become much harder to be a successful serial killer as technology and forensic science have improved alongside cameras (surveillance, ring cams, etc.) becoming practically ubiquitous. >

The majority of gun deaths in the US are from suicide. It just dawned on me that the other numbers can probably be attributed to suicidal people who just want to take other people down with them. Yikes. >

Thats 1000% what is happening. The question we need to be asking is why do so many people feel so hopeless that they want to die in the first place, and why are they so angry that they want to bring innocent people with them?