It's more down to the refs discretion more than anything else, it could be as little as one ball. If someone is noticably trying to exit the field and a player turns his gun on him, it's overshooting. If the situation was how you described it though, it seems a little over zealous. Also, it doesn't really make a difference where it hits, let's be honest a ref isn't going to have the time to sit a guy down, examine and count the hits on him, work out how many guns were on the field and then make a call.