Concealed weapons permit holder trying to stop armed robbery unintentionally shoots and kills store clerk

On May 17th, two armed robbers burst into a Family Dollar store in Houston, Texas. They locked the front door and put a gun to store clerk Tyrza Smith's head.
According to reports, Tyrza was cooperating with the robbers when a store customer, who had tried to leave but found the door lock, pulled out a handgun and proceeded to get into a gunfight with the robbers.
Tyrza was caught in the crossfire and was shot and killed. No one else was injured. The customer had a concealed weapons permit and according to ballistics, he was the one who shot and killed Tyrza.
20-year-old Dwight Richardson has been arrested and charged with the robbery. Police are still searching for the other suspect.
No decision has been made yet whether to charge the customer in the death of Tyrza. Even if he doesn't face criminal charges he could still be sued in civil court.