Actually I was thinking of two cases, one in the 1970s and another in the 1980s, where cap and ball revolvers were used in shootings. I read about the incidents on a gun forum a couple of years ago.
Not to be picky but cap and ball revolvers are “muzzleloaders” - the are multipleShot black powder weapons that load to the front of the cylindser. I have a bunch of them.
A muzzleloader would be a musket or a Pennsylvania rifle or a Plains rifle or a Civil War .58 Springfield. Suspect nobody’s been killed on purpose by one of those puppies since the 1880s or so.