I wouldn't broadly apply that to all cops although it's definitely true with cops in high crime areas where they're conditioned to see the community as the enemy. Internal coverups among police departments are a major problem and my guess is with this particular officer a lot was swept under the rug before this happened.
The mental health of cops also have to be considered as they're on average more stressed, depressed, suicidal, etc. than the average worker in other occupations and less likely to seek help.