Here is a little bit about bullies.
What all bullies have in common is the use of power to satisfy one’s own psychological shortcomings. Each time a bully moves against someone weaker, he/she feels better about themselves for an instant. But because that feeling doesn’t last, they do it again and again. Sometimes the bully appears to lack insight into their own behavior (unwitting bully), but more often the bully does know but elects to ignore the moral and ethical considerations by which the majority of people are bound. The rules don’t apply to them. Or they have projected so much self-hatred on the other that they truly believe that those they are bullying deserve exactly what they are getting.
To read more please visit http://www.goodtherapy.org/blog/adult-bullies/
This site provides good information about warning signs of a bully. Be sure to visit the site to learn about the warning signs.