I'm not too sure about the US Justice system, but to legally shoot someonen, they themselves have to be armed before you can get off the hook with reasonable force.
For home defence use Slugs to minimize the damage to surrounding houses, your house etc.
Go to any shooting range, they will probably help you out with finding a safetey course.
Up in the great white north we have to take saftey courses before we can even get near buying guns
