The story realy has nothing to do with the post office, that is just where it took place. From what I've heard on the news, a man was standing in line at the post office with a woman when another man walked in, walked up to the guy standing in line, and punched him in the face. The shooter, pulled a gun, fired one shot into the guy that hit him, and then left the post office.

It was more than likely an illegal weapon, but I don't know if I would call it an unjustified shooting.