As staff members we try to respond to every report we can see, but as Cash said they might not get reported in the first place. but rest assured that the staff team is doing the best they can to enforce all rules on everyone.
Sometimes we get reports where a bystander would report a cop for shooting someone else and saying : Shooting non threat. without mentioning who they shot which makes it even harder for us to figure out what happened.
Sometimes there wouldn't be enough evidence to punish someone, and we can't punish people with out concrete evidence.
To help us out getting everything in control you could record your gameplay and report on forum and you can also be more specific on the report details if you report them in game.