Indeed. In my home town we had a lady nicknamed Bloody Mary. A relative of some sort on my father's side in fact. She lived alone in a big old house near the edge of town. She had goats and other critters, but no electricity. College and high school kids used to harrass her. She started out using rock salt, and that sufficed for many years, with no harm done, except to few areas of exposed skin, since they never got very close to the house, being stupid but not that stupid. Then the harrassers got bolder, until she put a few rounds of .22 into their cars. That pretty well stopped the harrassment. However by that time she was getting pretty old, and pretty frazzled too. One night a transient decided that old dark house would be a good place to break into, maybe spend the night. Big mistake. She blew his head off as he was coming in the window by the bottom of the stairs. I don't know just what she had loaded in that old double, but I don't think it was rock salt.
I don't know about that. I didn't want to dispute wooly mammoth because I've never shot rock salt at plywood or a "good" leather jacket, but I don't see why a properly placed load of rock salt at a range under 10 yards wouldn't either take someone's head off, or come close enough to it for government work. At that range, it's still pretty much in the configuration of a slug.
The reason I say that is because I once shot reflexively at a doe that jumped up right in front of me in a corn field with a load of #6 while pheasant hunting, and dropped her dead in her tracks with a head shot. Not proud of it, and I hasten to add that I reported myself to the local constabulary right after I field dressed her. He was so shocked that I reported myself for a game violation that he didn't even write me up, and let me keep the meat to boot. 'Course, I had to promise I wouldn't go deer hunting during that year's season. :-)