A bully usually behaves differently toward persons of higher authority than to the target person. That is no different from the school yard bully who pushes someone to the ground and then turns to smile at the teacher standing nearby.

In today's workplace, most bullies behave in ways that are subtle, not blatantly aggressive. They have learned, like people who discriminate based on race, that little things done over a period of time are often more frightening and intimidating than would be stepping over the line of legality into a major confrontation. Bullies don't want to be caught. They don't wish to be held accountable for much of anything. Any behavior that they are called to account for will be blamed on someone else, usually the target person. They know how to explain things so they sound reasonable and logical, all the while, thinking about ways to increase the pain felt by their target.

It's not ordinarily one thing. It is usually a collection of events and interactions over a period of time that can range from a few days to months or years. A lot depends on the target's ability to withstand the onslaught of negative feelings created by such treatment

How Can You Tell if You Have a Bully in Your Workforce?
Well, turnover is a key indicator. It is hard for an employer to retain people in an environment where a bully is actively at work hurting others. Since there are so few satisfying outcomes available to employees who find themselves targets of a bully, the most often used escape mechanism is to quit the job.