What Happened to the Shooters?

The massive amount of shootings we have been experiencing is very disturbing. And...

I THINK ITS IMPORTANT TO GET TO THE CORE OF THE PROBLEM
SO THAT WE CAN DO A BETTER JOB WITH PREVENTION. 

What closed the shooters hearts and/or made them so hateful to begin with? What really drove them to it? I think there are many accurate answers that include things like, witnessing hate rhetoric or acts in admired people, exposure to violent games and movies or websites at a young age, various types of torture or abuse, mind control, microwave targeting...etc. And...

I think that, in many situations, the shooters had experienced a harmful lack of love and a lack of exposure to true kindness and consideration for fellow human beings. Humanity has a lot of healing work to do and cleaning up to do and... it must be done soon for the sake of the children - humanity's future.