In real life, Police are not judge jury and executioner. They are supposed to, in all but the most dire and dangerous circumstances, arrest even the most terrible Complete Monsters
and bring them to justice within the court system. Much of their job is finding non-violent resolutions to potentially violent situations. A cop who shot first and asked questions later would find himself unemployed at best, and in prison at worst.
However, in fiction, police are often employed as a death squad, shooting suspects without so much as trying to arrest them or find a non-violent resolution. It's uncommon that anyone seems to mind the massive levels of Police Brutality
and huge death tolls along with the brazen disregard for anything even resembling a criminal justice system. The Police Death Squad is even seen as noble sometimes, despite shooting up entire communities to get one guy accused of an often petty crime.