Emotion is what drives to do things. The desire for things, jealously, rage, good feelings. It lets us be “human”. At the same time, it can also cause us to things we may end up regretting or things that we normally would not do were it not for a certain emotional state. There are some professions which discourage being overly emotional. Any mistakes can give a bad name to the organization they represent or cause much liability. One such case are police officers, who have a history of brutality against suspects. This is illegal of course, but cops are humans too. When the suspect does something they do not like, such as harming a fellow brother, or the police officer is in an exceptionally bad mood, it is easy for anger to flare out. Sometimes, this can manifest into physical action, and that can have bad consequences.
Luckily, there may be people around to calm them down and not allow them to stew in their thoughts of rage.