The Police is one of the main factions in the series. They were Henry's main enemies in the first three games.
Police troops are usually armed with pistols or AK-47 assault rifles. Police officers can be recognized by blue caps and golden signs on them. That's how mostly all police officers in the Prison look like. The chief of the prison has a black hat.
Night security guards are guards of the Museum. They wear black hats with S letters on them. They work with police to stop Henry from stealing the diamond.
In Escaping the Prison and Stealing the Diamond, police officers drive cars. One of them is stolen by Henry in the Badass Ending. Later in Infiltrating the Airship, the same car can be seen in Henry's garage.