As a City Life Civilian, you are taking on a role (in the sense an actor has a role) and enacting or playing that character.
Mature behavior and language will be dictated by the situation you are involved in. Be aware if you are under the minimum age to play ARMA 3 you may be subjected to adult language.
If you have a weapon on display the Police can only assume you intend to use it to cause death or serious injury so expect to be met with lethal force. You have a holster, use it.
If you are running around towns with no other intent than to kill, then we will assume you no longer want to play City Life and could face a ban. Gunfights happen, and we understand that, however, keep in mind that normal cities are not war zones, and we are trying to treat this game as a real-life simulation.
We are not expecting you to all be saints if you don't do illegal things, then the Police won't have anything to do, but don't go too far.
Here are some refference links, which could be used in order to give you some ideas of what to do. And what can be done These are not all available examples!
City Life Police Department
Punching and Pushing
Hitman - Assassination
Offense Quick Reference Guide