Self defense from a Policeman.

[Jacobtm]

Say a policeman is overstepping his bounds, using excessive force with his club to subdue someone who is guilty of no crime.

Suppose this person has a firearm and shoots the police officer.

Is there a different standard for self defense here? If someone decided to start beating me with a club in public for no good reason, I assume that shooting them with a legal weapon would be an acceptable form of self-defense. But if its an officer, is one legally bound to take it?

[Jacobtm]

What about a different situation.

It's late at night, you (a homeowner) are asleep, you are awoken by the sound of someone noisily entering your house. You check and your whole family is asleep, and you shoot the intruder.

It was a police officer.

Any difference there?