if pertaining to murder, take a long distance (1,000 + yard) shot, then take the shell, file barrel, and dispose of gun in muriatic acid or white-hot flame. to add precaution, have a change of clothes, wear a prosthetic mask, colored contacts, fake scars/tattoos, dyed hair, etc when performing the hit.
either a scream mask for dramatic effect, or colored contacts, prosthetic masks, fake scars/tattoos, dyed hair/cut hair and reversible jackets (preferably change of clothes, but depending on job)
shoot from a very long distance (1,000 yards +) then file barrel and take shell, then dispose of gun itself in muriatic acid / white-hot flame. to add precaution, have change of clothes, colored contacts, fake scars/tattoos, dyed hair, etc.