If the owner goes along with it...you are now the security guard and manager! Otherwise it is still only a misdemeanor.....any conviction thats saves your life would be well worth it in my book......but that is just me!
According to the statutes that c3 just posted, getting written consent from the owner (which shouldn't be hard given the recent robbery across the street) should provide you with a legal avenue to follow.
No, you can't take my gun. I'm gonna need it when you try to take my truck...