This story doesn't smell right to me. It seems odd that a person would have to shoot a man and his wife in self defense.
It's too early to really tell what happened. It'll take a few days for the actual facts to make it to the papers.
I can envision one scenerio that would be plausible...No matter who dinged who's car door...No matter who started the argument...If the one guy with his wife grabs a metal pipe and starts beating the other guy over the head. The assualted guy goes down and knows he's being beaten, grabs his concealed weapon and without proper aiming just starts shooting in the direction of the attacker. With self preservation in mind he fires several times. The pipe wielder goes down and the woman takes a couple of slugs by just being there. That is self-defense.
But we don't know if it happened that way or not.