As a NRA Personal Protection Instructor I would strongly advise against using this store clerk as a role model. The robber appears to be leaving without harming anyone when she shoots him. This is generally illegal and I agree with this law. What I think happened was, as Joe D. suggested in email to the LPC email discussion list, it was an accidental discharge.
But on an strictly individual level I don’t have much sympathy for robbers, especially armed robbers. So, the bottom line is Barb and I laughed pretty hard at this guy getting “circumcised by a .38”: