One person can only take so much.  This employee is angry with his manager for something that happened (not sure what exactly) and has words with him.  The manager was getting a little close during the argument and the employee warned him to stay back.  Once the manager crossed the imaginary line the employee drew, it was over.  Even the other employee's saw it coming.  The one behind the camera was saying "don't hit him, don't hit him, don't hit him," at one point.