A woman just shot a gun in the parking lot of a store at a moving vehicle.  Yep, I think that qualifies for not understanding the risks.  I don't believe that is true of all gun owners, but it is definitely true of the woman's actions that you are defending.  She created an incredible risk that there may be an unlucky bystander.

Allowable by law does not mean you won't go to hell for murdering a person, you just may not be prosecuted by the State.  I think whoever wrote that law lacked humanity as well.  I also think you have misread the law after applying a bias that you should be able to kill person to protect your property and did not give a valid interpretation to the last part, "when another person, other than the perceived offender, is inside of the vehicle."  The story accuses both people in the vehicle as the offenders, so the law would not provide justification.