Cops are extremely trigger happy. They see something, they shoot. I don't even know why do they need tazers or handcuffs. Literally they just go on a 4 doors and pull the trigger on everything they see, even oranges. If you are a cop and don't do what i described don't be offended, as this is not being addressed to you. However, if you are a cop, then you definitely witnessed this going on.
And i know some here in the comments will say: "just report them" but that won't always solve the issue. If you ask me, we should have a direct, scripted penalty upon firing non most wanted criminals, subtracting Rank XP or the rank by itself without the need of staff intervention.