All guns have serial numbers. Any gun sold should not only be registered, but registered to the person who bought it by serial number. When they sell that gun, (as in straw purchasers who can pass a background check, but they buy guns to sell to people who can't pass a background check) and that gun is used in a crime or a mass murder, or any murder, the police go right to the registered owner. Apparently, we don't track a gun once it is sold. We do it with cars, and when a car is sold, we make sure the title is transferred to the buyer, so the seller doesn't get held liable if that car is in an accident, but we don't do it with guns when that gun might be used to murder someone?
That is insane.