I don't think we can say that all our police officers are corrupt. There are plenty of bad apples in the force but the majority of them are good people trying to keep us safe. Plus it's best not to jump to conclusions without a proper investigation. Maybe this particular retired cop is corrupt and dangerous but that needs to be investigated first.
As in all professions, there are people who will take advantage of their power and influence. The police have access to many tempting influences such as drugs and criminals, so they can be corrupted. The finding of a body on the police property still needs to be investigated before any assumptions are made.
Just as not all dogs are vicious, not all police officers are corrupt. However, the unquestioned authority and power that comes with being a police officer can turn a person to corruption. Corrupt cops have been a known issues for decades, across the world. Little can be done to stop it, it seems.
Police know that they have no accountability. When one of them does something terrible, the others just look the other way. There is no accountability. People go into law enforcement because they want to have the power to bully others without being held accountable for their actions. They commit assaults at very high rates, among other crimes.