The idea that it is morally acceptable to kill someone "taking your stuff" comes down to us from the distant past. A time when someone taking your "Stuff" could mean you and your family starved to death.
A time before insurance companies, FDIC and a social safety net. A time when there was no one, and nothing to help you survive, beyond family, friends, and the church's charity. When someone stole your stock, took your harvest, or the horse you needed to get that harvest, it was literally a death sentence to you and yours.
Therefore, killing the thieves was morally the right thing to do. What they did resulted in a death threat (slow, through starvation) to your family, so yes, they deserved what they got.
This situation still existed in our old west, to a degree, and was the recognized order of things, as they always had been. We hung horse thieves and cattle rustlers. We shot the bank robbers as they rode out of town with our money.
Why do you think ordinary citizens grabbed their guns and joined the posse going after the bank robbers?? Sure, it was the right thing to do, but why did they do it, when today most people wouldn't?
Because it was THEIR money that got stolen from the bank, and the ONLY way of having any hope of getting it back was to take it back from the people who stole it.
This is NOT the case today. Insurance, either private or government means there is a way of getting mere property (and money is just property) back. Society expects you to accept the loss, and file an insurance claim, rather than use deadly force to defend mere property.
Chasing a car thief gun blazing, hitting at least two neighborhood homes, and killing a grandma asleep in her house is simply totally wrong behavior. It is, however, the kind of thing we see "heroes" on TV do almost every night (minus they killing grandma part).
I can understand a guy, amped up by seeing his jeep taken, NOT THINKING beyond the immediate moment, doing what TV has "trained" him to do.
I can understand it. I cannot condone it, nor his poor marksmanship, which caused the death of an innocent individual.
The jeep can be replaced, Grandma cannot. 8 years may seem stiff, or not nearly enough, depending on your point of view.