You emphasize "private" property -- what does THAT mean -- as opposed to their PUBLIC property? You don't know WHAT you're talking about.
The only useful distinction re property in your example is your HOME, your domicile, versus some other property. Here we're talking about a commercial place of business. A presumption arises in some jurisdictions when you are protecting your HOME against intruders. That presumption does not arise when one's residence is not involved.
Certainly you can defend yourself against threat-of-physical-violence, wherever you are, but YOU insinuated on your earlier post that the use of deadly force in this instance is self-apparent, hence no prosection was justified. Huh? There are no impartial witnesses. The burglar was not even in possession of an unambigous weapon, as in a gun -- here he had a hammer only.
Could they have restrained the attacker without shooting to death? Were they angry about prior breakins and determined to kill the intruder (explaining why they were so heavily armed in their workshop -- did they 'always' have such guns around, for example?).
These are questions for a jury, where I come from.
While I do not deny there may be legal grounds for the charges, the article did not indicate such. WHATEVER HAPPENED TO COMMON SENSE!
Like people in all walks of life, there are those willing to advance their personal or political agendas by misusing their positions and authority, lawyers included. Education or position does not make one just or wise. While the letter of the law may be perfect, the exercise and execution is definitely not.
"explaining why they were so heavily armed in their workshop -- "
None of your business.
"did they 'always' have such guns around, for example?"
I certainly hope so.