> They should always kill the killer immediately in a most heinous way to discourage other killers. <
I wouldn’t go quite that far, but you do have a point. In the old West, it was quite easy to steal a horse. So vigilante groups started hanging horse thieves. And that did put a damper on the crime.
So perhaps the states should consider mass murder to be a hanging offense. But as you noted, the punishment would have to be relatively quick. Ten years after the fact just won’t do.
and put it on pay per view ...