You shouldn't be shooting an unarmed man, you only use deadly force to save your life or someone else's from eminent danger.
Possession of a knife or gun are not the only qualifiers for being "armed'... Sorry but I am not in the business of determining the level of violence a person is capable of dealing out... I am in the business of protecting my family. If a person makes entry into my home, they are living on limited moments.
The above is an unarmed person...
Anyone with limbs is also armed and potentially lethal or capable of causing GBH.