Should Police Be Required To Have Periodic Psychological Evaluations?

Police used to be called Peace Officers, and the intention was that they would maintain the peace. Today, the image of Officer Friendly helping a little lost child is long gone. Now social media sites are flooded with cell phone captured images of police brutally beating unarmed citizens into submission as observers watch in horror. This is not normal behavior. Perhaps labeling it as racism and racial profiling is too simplistic. Citizens in countries occupied by American troops abroad have voiced the same accusations of excessive brutality inflicted on citizens in the name of "keeping the peace" but it is this behavior that provokes violent reactions, distrust and hatred for American soldiers. The same distrust and hatred is being expressed toward police in many urban areas where complaints of police brutality seem to have escalated.  Does the job of controlling people using the threat of force create emotional distress that leads to excessive aggression? Can it lead an officer to "snap"? How do police department administrators recognize signs of "battle fatigue" in officers and pull them off of street duty? How many complaints of brutality is too many? Should officers be required to undergo periodic psychological examinations