If you think there's a chance of this happening to you, which there is, what are you doing to prevent it from happening, or to prepare for it if it does? I don't just mean carjacking, but all manner of assault.
The best defense is to avoid the situation in the first place, be aware of your surroundings, stay out of certain high-risk places, keep your car well maintained and gassed up, avoid being the victim as much as possible. Beyond that, learn to defend yourself, at least a little.
Here's a video called
Carjacking Defense Moves. I don't know if this would have helped in the particular situation being discussed, but at least it gets you thinking about options, instead of being resigned to be the victim.
(Sorry, I couldn't figure out how to imbed the video.)
There are lots of other self-defense videos on that site, but I haven't watched them.