well do you seriously plan to shoot him? Why would you even ask that? If hes randomly killing people then yes, he deserves to be shot, if not by you, then by someone else
Is this guy just walking down the street, and then he sees someone, whips out a gun and blasts them or what? and if so you should go on your roof and blast him from up there, preferrably in the back, before he ever sees it coming.