If someone were to walk into my family owned business and demand money (maybe wielding a weapon) at which point would it be lawful to neutralize him in Massachusetts? I really would have to hate to resort to that in result of living with the aftermath, courts, and the withdrawal of my weapon for evidence. I figured ignorance is one's worst enemy in these cases so I really would like to know fact and not opinion. Thanks
Although no ones knows what they would in fact do until they are in the situation you have to remember that no two situations are the same and no easy way to answer the question.
You stated that they "demand money (maybe wielding a weapon)"
You would have a hard time convincing someone that demanding money would justify deadly force If they do not have a weapon or give the indication that they have a weapon.
The type of weapon, the distance away that they are as well as the layout of the store (i.e. physical barriers etc..) would have an impact on the decision as well.
Your question contained part of the answer. Is the result of living with the aftermath, courts, lawsuits, scrutiny etc...worth the couple of hundred bucks in the register. Sometimes it is better to just give them the money and be the best witness you can be to help get them apprehended later on. Yes, there is a possibility that they still shoot you...Yes, there is also the possibility that the gun is a replica also, which is why you have to judge each situation seperately.
Invest in the best crime prevention methods that you can to help prevent being put into the situation in the first place (surveillence equip etc...). Invest in some firearms training that includes legal training on the use of force and remember that you must
ACTUALLY feel that your life is in danger and a reasonable person would also feel the same to be justified in the use of deadly force.
Cross-X also made a good point about less than lethal options as well.
These questions are not easy to answer. No one should be a victim but everyone should know the consequences of what they do before they do it.
just my $.02