Sorry, but the other person doesn't have to be armed with anything before you have the legal right to use deadly force.
I do not care about what is lawful. I only care for what is moral and nessecary.
If three or four thugs see you walking the street at night, scream "GET HIM" and start running at you, should you be prohibited from using your firearm to stop a brutal attack that could possibly mean your death?
I believe you should assess the situation and only fire as a last resort. You cannot justify massacring four people based on "could of been."
This is the problem we have today with the government goons. They piss their pants and go wild eyed bill the moment they feel the tiniest bit threatened.