I don't have an article for you to read, but I can share some personal experiences of things I have seen and experienced personally.

One of the worst bullies I ever knew seemed to be stuck in jr high, even though she was almost old enough for Social Security. I got the impression her life went off track about age 12 or 13 and she was flailing out at people she thought were the easiest targets to even the score.

Another bully I knew was an extremely angry alcoholic who appeared to have deep seated feelings of inadequacy going way back to his early childhood.

It is a form of violence to bully someone.