As you reach for the bag, you suddenly feel the muzzle of an extremely large gun against the side of your head. You haven't had much experience with this sort of thing before, but considering the width of it, you'd say...8 gauge. Minimum. With two barrels.
The guy holding it appears to be a 2 gauge, minimum, if such measurements can be applied to large, ungainly fellows with guns nearly bigger than they are.
"You're not leavin' here holding MY wall bag, thief. Or my umbrella. What you CAN do, though, is come upstairs and look at my latest creation. It is a marvel of modern technology, if I do say so myself. And I do. Although my experiment needs a new...test case."
He says modern technology, but you ARE concerned about the amount of filth covering his ragged clothing. Hopefully those stains are just motor oil.