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and this is just my opinion.
1st: It may have started as a property theft, but once the BG displayed and threatened another with a firearm, the situation was no longer about protecting a car.
2nd: If your not moving during a gun fight, your doing something wrong. You should be moving to gain a better position, cover, escape.
3rd: There is a lack of details from the story linked to come to a conclusion as to what really happened, or why.

On the surface, it does sound like the BG's chose the wrong sheep to carjack.