"I don't think any have got away with it that survived and most are looking at the rest of their lives in jail."
I forgot to address this point earlier, sorry. (Been loading hay all day and I am rather tired and not thinking as sharp as normally, which isn't all that sharp anyways XD
I don't think these guys will give an iota about going to jail. They will probably regard it as a party and that they will be feared and respected by other lesser known criminals in there. And they will be looking forward to bragging about their stack of kills among the other "greats" behind bars.
You may not find this story relevant but I think it speaks volume to the mindset of today's youth.
My sister has a friend (well former friend now she doesn't really hang around my sister anymore) who said she is now an atheist. And she said she is not concerned about Hell and that Hell will be just a big party. And her parents are church going Christians, I am sure she has had quite a vivid description of what hell will be like.
My point with that story is that people today, especially the younger generation, have no concern with abstract consequences. If the idea of Hell isn't enough to scare a teen into remaining true to their faith, what significance will the idea of jail time have on mass shooters? Especially if jail is as good as what I hear, they will not be phased by the thought of jail at all.
Now if jail was harsh brutal and they are able to see it with their own eyes, then that might make a difference. That is why I am throwing out my idea of a painful execution for people to witness. That way it will have much more impact on them.