Under Missouri's Stand Your Ground law, as outlined in Missouri Senate Bill 656 that went into effect 1/1/2017, if a person is in a place where they are permitted to be, they have the right to use deadly force to protect themselves or another innocent party, even if they potentially had the opportunity to safely retreat. That law applies whether the one using deadly force is on public or private property. Therefore, your question is irrelevant.
Under the law, the person using deadly force has to have a reasonable fear that the offender is threatening them or an innocent party with deadly force. Only the one defending him/herself with deadly force has the ability to make that determination. To say otherwise, would mean you believe someone else can read their mind.
It's OK. Governor Parsons has said if they are convicted, he'll pardon them.