Now, had he killed one or two of the youngest ones in the bunch, would it be justifiable (granted, their tribes would have a death vendetta toward him)?
A man from Arkansas took a wrong turn in Milwaukee a few months ago shot and killed a youth who was trying to rob him. Even though the Arkansas man had a loaded gun in his van which is highly illegal in Wisconsin, the man was released from custody the next day and no charges were filed. (Man won't be charged in gas station shooting)
Wisconsins laws are not particularly good when it comes to CCW and self-defense, but they are seldom used to prosecute people involved in clear self-defense shootings.