I recall Norman Mailer making the point that the mentality of most police is similar to that of the criminals. Maintenance of law and order requires people who are capable of being violent and strong enough to overcome resistance. The nature of the job attracts many people who enjoy physical violence and being able to use their physicality while being supported by the governing authorities. The extent to which police overstep the mark, so to speak, depends upon management and the prevailing culture of the society in which they function. As crime levels rise the tendency is for the general population to approve of increasingly violent levels of suppression.
Watching local TV news this morning and yet another story with a would be robber being beaten by a mob. It seems common for apprehended criminals to be paraded with legs bandaged and sometimes with the explanation that they were shot while trying to escape. Who knows how many extra-judicial police killings occur in Indonesia each year? In Kenya last year there were 118 extra judicial killings by police. When I was living there, during one six month period 800 thieves were beaten to death by mobs..